libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2_cipher_crypt() function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit the underflow in the expression computing blocksize minus aadlen minus authentication tag length to trigger an out-of-bounds read and a memcpy call with a near-SIZE_MAX length argument, causing immediate process crash before any authentication occurs.
1.8.0-11.8.0-1ubuntu0.11.8.0-2.1build11.8.0-2.1ubuntu0.11.10.0-21.10.0-2build11.10.0-31.9.0-31.11.0-4.1ubuntu0.24.04.41.11.1-1ubuntu0.26.04.41.4.3-11.4.3-21.4.3-2ubuntu0.11.4.3-2ubuntu0.21.4.3-2ubuntu0.2+esm11.4.3-2ubuntu0.2+esm21.4.3-2ubuntu0.2+esm31.5.0-21.5.0-2ubuntu0.11.5.0-2ubuntu0.1+esm11.5.0-2ubuntu0.1+esm2Exploitability
AV:NAC:LAT:NPR:NUI:NVulnerable System
VC:NVI:NVA:HSubsequent System
SC:NSI:NSA:NCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N