libssh2 publickey-subsystem Memory Safety Flaws

Heap buffer overflow in the libssh2 SSH client library (all versions through 1.11.1) lets a malicious or compromised SSH server corrupt memory in any connecting client on 32-bit platforms. The publickey subsystem reads an attacker-supplied 32-bit attribute count and multiplies it by the attribute structure size without bounds checking, so the allocation integer-overflows to an undersized buffer that the parsing loop then writes past. Publicly available exploit code exists; this is a CWE-190 integer overflow with no public exploit identified in CISA KEV, so it is not confirmed actively exploited.

Free of an uninitialized, attacker-influenceable pointer in libssh2 through 1.11.1 allows a malicious SSH server to corrupt memory in any connecting client that uses the publickey subsystem. The publickey list is grown via SSH2_REALLOC without zero-initializing new entries, so a server-induced parse failure that reaches the cleanup path causes libssh2_publickey_list_free to operate on an uninitialized attrs pointer. Publicly available exploit code exists (reported by VulnCheck); no public evidence of active exploitation, and it is not listed in CISA KEV.