Brandon Luo

A TLS server may experience an out-of-bounds read and a fixed-value out-of-bounds write on the server heap when calling the `SSL set SSL CTX()` function to switch a connection to a different SSL CTX during a handshake. This occurs if the replacement context recognizes more provider signature algorithms than the original context used to create the connection, as the internal array of per-slot certificate validity flags is not refreshed. A remote peer can trigger this by offering multiple signature algorithms, potentially corrupting heap metadata and causing a Denial of Service. This issue specifically affects provider signature algorithms usable from TLS 1.3.

An issue exists in the CMP response validation where the `ossl cmp msg check update()` function converts a peer-supplied sender distinguished name using `X509 NAME oneline()` and passes it directly as the format argument to `ERR raise data()`. Because percent characters are preserved during conversion, a malicious or intercepted CMP endpoint can provide a sender DN containing format specifiers like `%s` or `%n`. These specifiers reach `BIO vsnprintf()` without matching variadic arguments, causing the client to dereference or write through unrelated stack contents. This leads to a denial of service by crashing the CMP client, specifically when the client enforces an expected sender or uses a pinned server certificate.