CVE-2026-72897
HighCVSS 7.5Summary
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. 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, potentially leading to a Denial of Service.
Risk Assessment
The risk includes potential denial of service (DoS) via remote heap corruption. The vulnerability affects only applications using SSL_set_SSL_CTX() with contexts that differ in the number of provider signature algorithms, which is a non-default and uncommon configuration, but it could be exploited to crash the service.
Recommendation
It is recommended to update OpenSSL to a version containing the fix for CVE-2026-72897. If updating is not possible, avoid using SSL_set_SSL_CTX() with contexts that have different numbers of provider signature algorithms, or ensure the contexts have identical configuration.
Other vulnerabilities in OpenSSL
See all- CVE-2026-84784High
A malicious remote peer can flood the local QUIC stack with NEW_CONNECTION_ID frames by bypassing a limit on connection IDs. This causes RETIRE_CONN_ID frames to be sent and, with withheld ACKs, can allocate about 400 MB of memory.
- CVE-2026-84783High
OpenSSL 4.0 contains a use-after-free vulnerability (CWE-416) in the caching of X.509 certificate extensions. When several threads concurrently use the same certificate for the first time, one thread may free the cached extension data while another thread is still using it. This can crash the process, resulting in a Denial of Service.
- CVE-2026-84782High
The DTLS retransmission logic incorrectly handles a handshake message write that is suspended part-way through. The retransmitted message can be read past the message buffer, disclosing heap memory or causing a crash and Denial of Service.
- CVE-2026-77696Low
SM2 signature generation uses non-constant-time arithmetic on secret values, forming a timing side-channel. An attacker able to measure SM2 signing times may learn information about the per-signature secret nonce, which over many signatures can lead to recovery of the private key. Applications performing SM2 signature generation are affected on all platforms.
- CVE-2026-75806Medium
An established DTLS 1.2 association using an AEAD cipher suite can be terminated by a single unauthenticated datagram whose encrypted fragment is shorter than the mandatory explicit IV and authentication tag overhead. The record layer passes the record length to the cipher before checking it is long enough, causing an internal error instead of treating the record as failed authentication.
- CVE-2026-75805Medium
A NULL pointer dereference vulnerability in the OpenSSL CMP client. When a client requests certificate revocation based on a PKCS#10 CSR and the server returns a specially crafted certificate name in its response, the client reads from a NULL pointer and crashes. Only clients that identify the certificate via CSR (e.g. 'openssl cmp -cmd rr -csr' or OSSL_CMP_exec_RR_ses() with OSSL_CMP_CTX_set1_p10CSR()) are affected.
- CVE-2026-75804Medium
The OpenSSL QUIC stack does not enforce connection-level flow control for streams. A malicious remote peer can send more bytes as long as they fit within stream flow control limits, leading to excessive memory allocation.
- CVE-2026-54875Low
OpenSSL's optimized scalar point multiplication implementation for SM2 private key operations on ARM64 and RISC-V platforms is not constant-time. Conditional branches and table lookups depend on the bits of the secret scalar, so execution time and cache-access patterns leak information about the private key or signature nonce.
- CVE-2026-54873High
A vulnerability in the QUIC implementation in OpenSSL allows a remote attacker to keep allocated packet buffer memory for an extended period by sending specially crafted packets. The issue stems from missing resource allocation limits (CWE-770), potentially leading to excessive memory consumption.
- CVE-2026-54872Low
The generic elliptic-curve scalar multiplication used for ECDSA and SM2 signature operations with curves lacking a dedicated implementation leaks information about the secret nonce through timing. An attacker measuring signing times may learn the nonce, which over many signatures can lead to private key recovery.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS