| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| The OpenSSL 3.0 implementation of the RC4-MD5 ciphersuite incorrectly uses the AAD data as the MAC key. This makes the MAC key trivially predictable. An attacker could exploit this issue by performing a man-in-the-middle attack to modify data being sent from one endpoint to an OpenSSL 3.0 recipient such that the modified data would still pass the MAC integrity check. Note that data sent from an OpenSSL 3.0 endpoint to a non-OpenSSL 3.0 endpoint will always be rejected by the recipient and the connection will fail at that point. Many application protocols require data to be sent from the client to the server first. Therefore, in such a case, only an OpenSSL 3.0 server would be impacted when talking to a non-OpenSSL 3.0 client. If both endpoints are OpenSSL 3.0 then the attacker could modify data being sent in both directions. In this case both clients and servers could be affected, regardless of the application protocol. Note that in the absence of an attacker this bug means that an OpenSSL 3.0 endpoint communicating with a non-OpenSSL 3.0 endpoint will fail to complete the handshake when using this ciphersuite. The confidentiality of data is not impacted by this issue, i.e. an attacker cannot decrypt data that has been encrypted using this ciphersuite - they can only modify it. In order for this attack to work both endpoints must legitimately negotiate the RC4-MD5 ciphersuite. This ciphersuite is not compiled by default in OpenSSL 3.0, and is not available within the default provider or the default ciphersuite list. This ciphersuite will never be used if TLSv1.3 has been negotiated. In order for an OpenSSL 3.0 endpoint to use this ciphersuite the following must have occurred: 1) OpenSSL must have been compiled with the (non-default) compile time option enable-weak-ssl-ciphers 2) OpenSSL must have had the legacy provider explicitly loaded (either through application code or via configuration) 3) The ciphersuite must have been explicitly added to the ciphersuite list 4) The libssl security level must have been set to 0 (default is 1) 5) A version of SSL/TLS below TLSv1.3 must have been negotiated 6) Both endpoints must negotiate the RC4-MD5 ciphersuite in preference to any others that both endpoints have in common Fixed in OpenSSL 3.0.3 (Affected 3.0.0,3.0.1,3.0.2). |
| The function `OCSP_basic_verify` verifies the signer certificate on an OCSP response. In the case where the (non-default) flag OCSP_NOCHECKS is used then the response will be positive (meaning a successful verification) even in the case where the response signing certificate fails to verify. It is anticipated that most users of `OCSP_basic_verify` will not use the OCSP_NOCHECKS flag. In this case the `OCSP_basic_verify` function will return a negative value (indicating a fatal error) in the case of a certificate verification failure. The normal expected return value in this case would be 0. This issue also impacts the command line OpenSSL "ocsp" application. When verifying an ocsp response with the "-no_cert_checks" option the command line application will report that the verification is successful even though it has in fact failed. In this case the incorrect successful response will also be accompanied by error messages showing the failure and contradicting the apparently successful result. Fixed in OpenSSL 3.0.3 (Affected 3.0.0,3.0.1,3.0.2). |
| An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signature_algorithms extension (where it was present in the initial ClientHello), but includes a signature_algorithms_cert extension then a NULL pointer dereference will result, leading to a crash and a denial of service attack. A server is only vulnerable if it has TLSv1.2 and renegotiation enabled (which is the default configuration). OpenSSL TLS clients are not impacted by this issue. All OpenSSL 1.1.1 versions are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j). |
| In situations where an attacker receives automated notification of the success or failure of a decryption attempt an attacker, after sending a very large number of messages to be decrypted, can recover a CMS/PKCS7 transported encryption key or decrypt any RSA encrypted message that was encrypted with the public RSA key, using a Bleichenbacher padding oracle attack. Applications are not affected if they use a certificate together with the private RSA key to the CMS_decrypt or PKCS7_decrypt functions to select the correct recipient info to decrypt. Fixed in OpenSSL 1.1.1d (Affected 1.1.1-1.1.1c). Fixed in OpenSSL 1.1.0l (Affected 1.1.0-1.1.0k). Fixed in OpenSSL 1.0.2t (Affected 1.0.2-1.0.2s). |
| There is an overflow bug in the x64_64 Montgomery squaring procedure used in exponentiation with 512-bit moduli. No EC algorithms are affected. Analysis suggests that attacks against 2-prime RSA1024, 3-prime RSA1536, and DSA1024 as a result of this defect would be very difficult to perform and are not believed likely. Attacks against DH512 are considered just feasible. However, for an attack the target would have to re-use the DH512 private key, which is not recommended anyway. Also applications directly using the low level API BN_mod_exp may be affected if they use BN_FLG_CONSTTIME. Fixed in OpenSSL 1.1.1e (Affected 1.1.1-1.1.1d). Fixed in OpenSSL 1.0.2u (Affected 1.0.2-1.0.2t). |
| Simultaneous Multi-threading (SMT) in processors can enable local users to exploit software vulnerable to timing attacks via a side-channel timing attack on 'port contention'. |
| The OpenSSL ECDSA signature algorithm has been shown to be vulnerable to a timing side channel attack. An attacker could use variations in the signing algorithm to recover the private key. Fixed in OpenSSL 1.1.0j (Affected 1.1.0-1.1.0i). Fixed in OpenSSL 1.1.1a (Affected 1.1.1). |
| The OpenSSL DSA signature algorithm has been shown to be vulnerable to a timing side channel attack. An attacker could use variations in the signing algorithm to recover the private key. Fixed in OpenSSL 1.1.1a (Affected 1.1.1). Fixed in OpenSSL 1.1.0j (Affected 1.1.0-1.1.0i). Fixed in OpenSSL 1.0.2q (Affected 1.0.2-1.0.2p). |
| During key agreement in a TLS handshake using a DH(E) based ciphersuite a malicious server can send a very large prime value to the client. This will cause the client to spend an unreasonably long period of time generating a key for this prime resulting in a hang until the client has finished. This could be exploited in a Denial Of Service attack. Fixed in OpenSSL 1.1.0i-dev (Affected 1.1.0-1.1.0h). Fixed in OpenSSL 1.0.2p-dev (Affected 1.0.2-1.0.2o). |
| In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call. This can lead to a buffer overflow when EVP_PKEY_decrypt() is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated. Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k). |
| The X509_V_FLAG_X509_STRICT flag enables additional security checks of the certificates present in a certificate chain. It is not set by default. Starting from OpenSSL version 1.1.1h a check to disallow certificates in the chain that have explicitly encoded elliptic curve parameters was added as an additional strict check. An error in the implementation of this check meant that the result of a previous check to confirm that certificates in the chain are valid CA certificates was overwritten. This effectively bypasses the check that non-CA certificates must not be able to issue other certificates. If a "purpose" has been configured then there is a subsequent opportunity for checks that the certificate is a valid CA. All of the named "purpose" values implemented in libcrypto perform this check. Therefore, where a purpose is set the certificate chain will still be rejected even when the strict flag has been used. A purpose is set by default in libssl client and server certificate verification routines, but it can be overridden or removed by an application. In order to be affected, an application must explicitly set the X509_V_FLAG_X509_STRICT verification flag and either not set a purpose for the certificate verification or, in the case of TLS client or server applications, override the default purpose. OpenSSL versions 1.1.1h and newer are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1h-1.1.1j). |
| Server or client applications that call the SSL_check_chain() function during or after a TLS 1.3 handshake may crash due to a NULL pointer dereference as a result of incorrect handling of the "signature_algorithms_cert" TLS extension. The crash occurs if an invalid or unrecognised signature algorithm is received from the peer. This could be exploited by a malicious peer in a Denial of Service attack. OpenSSL version 1.1.1d, 1.1.1e, and 1.1.1f are affected by this issue. This issue did not affect OpenSSL versions prior to 1.1.1d. Fixed in OpenSSL 1.1.1g (Affected 1.1.1d-1.1.1f). |
| Issue summary: A malicious remote peer may flood the local QUIC
stack with NEW_CONNECTION_ID frames by avoiding a limit check on
how many connection IDs the remote QUIC stack can use.
Impact summary: The local QUIC stack sends a RETIRE_CONN_ID frame
for every NEW_CONNECTION_ID frame it receives. The RETIRE_CONN_ID
frame is dispatched via the Control Frame Queue (CFQ). If the remote
peer also withholds ACKs, then it can force the local stack
to allocate ~400MB (depending on ACK delay).
CWE: CWE-770: Allocation of Resources Without Limits or Throttling
Description: RFC 9000 sections 5.1.1 and 5.1.2 [1] describe the mechanism
by which a remote peer can notify the local QUIC stack to change the
destination connection ID (a.k.a. CID) the local stack uses to
identify the connection at the remote peer. Each CID is associated
with a sequence number. The sequence number is transmitted
in NEW_CONNECTION_ID and RETIRE_CONNECTION_ID frames to identify the CID
which is being either associated with a connection or retired.
The remote peer sends a NEW_CONNECTION_ID frame to let the local stack know
a new CID is being associated with an existing connection. The
NEW_CONNECTION_ID frame carries the new CID, its sequence number, and the
retire-prior-to number. The retire-prior-to identifies existing
CIDs that are to be retired. The local QUIC stack must send a
RETIRE_CONNECTION_ID for every destination CID whose sequence number
is less than retire-prior-to. The CID becomes retired after the
local stack receives an ACK for its RETIRE_CONNECTION_ID frame.
Although the OpenSSL QUIC stack supports at most one destination CID
for every connection, it can be tricked into processing more than
one RETIRE_CONNECTION_ID frame per connection. The OpenSSL QUIC
stack currently retires the destination CID as soon as it receives
the NEW_CONNECTION_ID, while in fact the destination CID must
be retired after an ACK for the RETIRE_CONNECTION_ID frame is received.
Correcting the flawed logic also fixes the backlog growth.
[1] https://datatracker.ietf.org/doc/html/rfc9000#name-issuing-connection-ids
FIPS impact: no
The FIPS module is not affected as the QUIC implementation is outside of
the OpenSSL FIPS module boundary. |
| Issue summary: The first concurrent use of the same X.509 certificate by
several threads may cause its cached extension data to be freed while
another thread is still using it.
Impact summary: A remote, unauthenticated peer could crash a multi-threaded
TLS client, or a multi-threaded TLS server that requests client
certificates, if the first certificate chains built to the same trusted CA
certificate are built by several connections at the same time. This is a
use-after-free read, which is likely to crash the process, resulting in a
Denial of Service.
CWE: CWE-416: Use After Free
Description: OpenSSL caches the decoded values of a certificate's X.509v3
extensions inside the X509 object the first time they are needed. In
OpenSSL 4.0 this cache is built in two phases: the extension values are
computed while holding a read lock on the certificate, and the results are
then installed into the certificate under a write lock. Because a read lock
does not exclude other readers, several threads can compute the cache for
the same certificate at the same time. Each thread that subsequently
acquires the write lock installs its own results and frees the values
installed by the thread before it, even though that earlier thread has
already marked the cache as complete and may have returned pointers into it
to its caller. A caller still using those pointers then reads freed memory.
Any certificate shared between threads is exposed the first time its
extensions are decoded. In TLS the certificates at risk are the trusted CA
certificates supplied for chain verification, by whatever means, since these
are shared by every connection and their extensions are decoded and cached
the first time a chain is built to them. Certificates sent by the peer are
decoded separately for each connection and are not shared, so they are not
affected. In a TLS client verifying server certificates, or a TLS server
that requests and verifies client certificates, the use-after-free could
only occur if the first chains built to the same trusted CA are built by
several connections at the same time.
FIPS impact: no
The FIPS module is not affected as X.509 certificate handling is outside
of the OpenSSL FIPS module boundary.
OpenSSL 4.0 is vulnerable to this issue.
OpenSSL 3.6, 3.5, 3.4, 3.0, 1.1.1 and 1.0.2 are not affected by this issue.
OpenSSL 4.0 users should upgrade to OpenSSL 4.0.3.
This issue was reported on 27 August 2026 by Tim Becker (Xint.io) and
independently in a public report on 31 August 2026 by aydinmercan.
The fix has been developed by Bob Beck.
-- cut (non-publishing metadata for internal use) --
Reported by: Tim Becker (Xint.io), aydinmercan
Fixed by: Bob Beck |
| Issue summary: OpenSSL QUIC stack does not enforce connection
level flow control for streams. Remote peers may send more bytes
as long as they fit within the stream flow control limits.
Impact summary: A malicious remote peer may exploit the lack of connection
flow control for streams to make the QUIC stack receive ~100MB of memory
instead of 768 KiB (default flow control window size).
CWE: CWE-770: Allocation of Resources Without Limits or Throttling
Description: The local QUIC stack advertises two flow control limits
to its remote peer: stream flow control limit and connection flow
control limit. The remote peer must follow both limits when transmitting
stream data.
Whenever the local QUIC stack receives a stream frame, it validates
that the size of the received stream frame stays within flow control limits.
If either limit is exceeded (stream level or connection level), then
the QUIC stack must close the connection with a flow control error.
The vulnerable OpenSSL QUIC stack enforces the stream-level but not
the connection-level limit. To exploit the issue, three conditions must be met:
- the remote peer opens several streams
- each stream must stay within the stream-level flow control limit
- there must be no zero-offset byte sent on any of the streams
(to prevent the vulnerable QUIC stack from consuming data).
By meeting the conditions above, the remote peer may make the local stack
allocate 2 x MAX_STREAMS x (stream flow control limit) bytes
of memory. MAX_STREAMS defaults to 100, and the limit applies to both
bidirectional and unidirectional streams, making it 200 in total. The default
flow control window for a stream is 512kB. The remote peer may
force the vulnerable QUIC stack to allocate 100MB of heap per connection.
FIPS impact: no
The FIPS module is not affected as the QUIC implementation is outside of
the OpenSSL FIPS module boundary. |
| Issue summary: A TLS server that calls SSL_set_SSL_CTX() to switch a
connection to a different SSL_CTX part way through a handshake may access
memory beyond the end of an internal array if the replacement context knows
about more provider signature algorithms than the context the connection was
created from. Applications which never call SSL_set_SSL_CTX() are not
affected.
Impact summary: A remote peer may be able to cause a small out-of-bounds
read, and in some circumstances a fixed-value out-of-bounds write, on the
server heap. This may lead to a Denial of Service.
CWE: CWE-787: Out-of-bounds Write
Description: A TLS connection records how many certificate slots it has
when it is created, taken from the SSL_CTX that created it: the built-in
certificate types plus one slot for each provider TLS-SIGALG entry that
context was aware of. That count sizes an internal array of per-slot
certificate validity flags.
An application may replace a connection's SSL_CTX part way through the
handshake by calling SSL_set_SSL_CTX(), most commonly from a servername
callback in order to serve a different virtual host. Doing so did not
refresh the recorded count. A provider signature algorithm's slot index is
its position in the list of whichever context resolves it, so if the
replacement context is aware of more of them than the original, an
algorithm offered by the peer can resolve to an index beyond the end of the
array. Processing the peer's signature algorithms then reads one four byte
word past the end for each such algorithm and, where the word read is zero,
writes a fixed value over it. A peer offering many of them can corrupt heap
metadata and abort the process.
Only provider signature algorithms which occupy one of the excess slots,
and which the server also has configured, have this effect. Codepoints the
replacement context does not recognise are discarded without being resolved
to a slot, and provider signature algorithms are usable only from TLS 1.3.
The two contexts must therefore be aware of different numbers of provider
signature algorithms, which requires separate library contexts, a provider
loaded between the two being created, or providers which differ in what
they advertise - in 4.0, for example, the default provider advertises SM2
where the FIPS provider does not. A deployment meeting the condition is
also unable to negotiate the affected algorithms with legitimate clients,
since the same stale count hides the corresponding certificates, so the
misconfiguration is likely to be noticed. For that reason, and because the
configuration is not the default, this issue has been assessed as Low
severity.
FIPS impact: no
No FIPS modules are affected by this issue as the affected code is outside
the OpenSSL FIPS module boundary. |
| Issue summary: A non-constant-time optimized implementation of scalar
point multiplication is used for SM2 private key operations on ARM64 and
RISC-V platforms.
Impact summary: An attacker able to measure the time taken by, or to observe
the cache-line access pattern of SM2 signing or decryption on an affected
platform can learn information about the secret scalar.
CWE: CWE-208: Observable Timing Discrepancy
Description: On ARM64 and RISC-V processors, the SM2 curve uses an optimized
scalar multiplication implementation whose conditional branches and table
look ups are chosen according to the bits of the secret scalar. The execution
time and the cache-access pattern therefore depend on the long-term private
key (during SM2 decryption) or the per-signature nonce (during SM2 signature
generation), forming a timing and cache side-channel.
FIPS Impact: no
SM2 is not a FIPS algorithm and the optimized SM2 implementation is not part
of the FIPS module.
OpenSSL 4.0, 3.6, 3.5 and 3.4 are vulnerable to this issue on AArch64 and
RISC-V.
OpenSSL 3.0, 1.1.1 and 1.0.2 are not affected by this issue.
OpenSSL 4.0 users should upgrade to OpenSSL 4.0.3.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.5.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.9.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.8.
This issue was reported on 2 May 2026 by Abhinav Agarwal.
It was independently reported on 6 June 2026 by Feng Xue.
The fix was developed by Igor Ustinov.
-- cut (non-publishing metadata for internal use) --
Reported by: Abhinav Agarwal, Feng Xue
Fixed by: Igor Ustinov |
| Issue summary: QUIC process may keep memory for QUIC packet
buffer for much longer period than necessary.
Impact summary: Remote peer can exploit this vulnerability
by sending maliciously crafted packets, making the local
QUIC stack to keep the memory for packet buffers allocated.
The time for which the memory remains allocated is entirely
under the control of the potentially malicious remote peer.
CWE: CWE-770: Allocation of Resources Without Limits or Throttling
Description: To save copy operation from the packet buffer to the
stream reassemble buffer the QUIC stack leaves the stream data
on the packet buffer waiting to be copied to a buffer provided
by the local receiving application. The QUIC stack releases
a reference to the packet buffer only after the data are copied
to the application buffer. This design is more efficient for
legitimate data transfers but enables an attacker to allocate a lot
more memory than actually required by the data kept in the receiving
stream buffer.
To mitigate the vulnerability, the QUIC stack now calculates
and monitors memory overhead for every stream. The memory overhead
for a single stream frame is calculated as a difference between the
size of the whole packet that carries the stream frame and the size
of the stream frame itself. The memory overhead for a single stream
frame is added to the total (cumulative) memory overhead QUIC stack
keeps for each stream. Once the cumulative memory overhead exceeds
64kB, the QUIC stack moves the stream frame data from the packet
buffer to the stream buffer, starting with the next packet received.
FIPS impact: no
The FIPS module is not affected as the QUIC implementation is outside of
the OpenSSL FIPS module boundary. |
| Issue summary: The QUIC stream reassembly algorithm performance deteriorates
progressively as packets are arriving out of order. The worst case has
a quadratic complexity proportional to the number of stream frames kept in
the buffer for the received stream data.
Impact summary: A remote QUIC peer that completes the handshake can create
a connection-scoped CPU pressure and potentially a Denial of Service using
compliant STREAM frames inside the advertised receive window, with low
attacker bandwidth.
CWE: CWE-407: Inefficient Algorithmic Complexity
Description: OpenSSL manages received QUIC stream fragments using a
doubly-linked list. While it optimizes for append operations (at the end of
the list), it falls back to a head-to-tail linear search for any fragment
that does not immediately follow the current `tail`.
By manipulating the sequence of offsets, an attacker can force the server
to perform O(n^2) operations, consuming excessive CPU time for the
QUIC process.
FIPS impact: no
The FIPS module is not affected as the QUIC implementation is outside of
the OpenSSL FIPS module boundary. |
| Issue summary: The OpenSSL QUIC server, when configured to not preform address
validation, can be forced to count incoming packets multiple times in its
unvalidated credit computation, leading to a violation of the RFC 9000
unvalidated connection amplification limit of 3 times the amount of data
received.
Impact summary: A remote attacker able to spoof packets to a server using the
OpenSSL QUIC implementation might use the server for an amplification of
a DDoS attack.
CWE: CWE-440: Expected Behavior Violation
Description: OpenSSL's QUIC stack, when operating as a server, enforces client
address validation (RFC 9000, Section 8), to confirm the peer address is not
used for a traffic amplification attack. If this feature is disabled on the
server, the QUIC stack limits the amount of server data that can be sent to 3
times the amount of data received from the peer address, until such time as the
TLS handshake is completed.
The OpenSSL QUIC server, when operating in non-validation mode, adds the
length of the whole datagram received to the unvalidated credit limit when
processing each QUIC packet in the datagram. A remote peer may,
after establishing a connection with an initial client hello frame, send a
subsequent datagram containing multiple QUIC packets, leading the server to
account the entire datagram length for each packet in the datagram, resulting
in the server believing that the peer has sent more data than it actually has,
thereby violating the 3x amplification limit mandated by the RFC.
FIPS impact: no
As the QUIC stack lives outside the FIPS module boundary, no FIPS modules
are affected by this CVE. |
