A TLS server that switches contexts during a handshake by calling SSL_set_SSL_CTX can end up accessing memory beyond an internal array when the new context knows more provider signature algorithms than the original. This mismatch allows a remote attacker to trigger a small out‑of‑bounds read and, in certain cases, a fixed‑value write on the heap, potentially corrupting heap metadata and aborting the process. The primary consequence is a denial of service because the server crashes.

The vulnerability affects installations of the OpenSSL library where SSL_set_SSL_CTX is used, typically in servername callbacks that serve virtual hosts. Any OpenSSL build that supports provider signature algorithms and can change contexts during a handshake is subject, regardless of the OpenSSL version because the condition depends on the configuration and presence of multiple provider contexts.

The CVSS score of 7.5 indicates moderate severity, and the EPSS score is not available; the issue is not listed in CISA’s KEV catalog. Exploitation requires a client that advertises many provider signature algorithms and the ability to trigger a context switch, so the attack vector is through a normal TLS handshake. Although not a default misconfiguration, honest deployments that satisfy the condition are likely to notice the problem due to failed negotiations, lowering the likelihood of widespread exploitation, yet the potential for denial of service remains.