Out-of-bounds Read Affecting libssh2 package, versions *


Severity

Recommended
low

Based on Debian security rating.

Threat Intelligence

EPSS
0.58% (46th percentile)

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  • Snyk IDSNYK-DEBIAN13-LIBSSH2-18300251
  • published25 Jul 2026
  • disclosed24 Jul 2026

Introduced: 24 Jul 2026

CVE-2026-66033  (opens in a new tab)
CWE-125  (opens in a new tab)
CWE-191  (opens in a new tab)

How to fix?

There is no fixed version for Debian:13 libssh2.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libssh2 package and not the libssh2 package as distributed by Debian. See How to fix? for Debian:13 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1