VULNERABILITY INTELLIGENCE

CVE-2026-66033

CVSS score7.5 HIGH
EPSS probability0.58%
CISA KEVNot currently listed
Published2026-07-24
Last modified2026-07-30
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Description

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.

Weakness classification

  • disclosure@vulncheck.com: CWE-125

Primary references