Out-of-bounds Read Affecting libssh2 package, versions [0,]
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-CONAN-LIBSSH2-21248785
- published19 Oct 2026
- disclosed24 Jul 2026
- creditUnknown
Introduced: 24 Jul 2026
CVE-2026-66033 (opens in a new tab)How to fix?
A fix was pushed into the master branch but not yet published.
Overview
Affected versions of this package are vulnerable to Out-of-bounds Read via the ssh2_cipher_crypt function during AES-GCM cipher negotiation. An attacker can cause a client process to crash by operating a specially crafted, untrusted SSH server that triggers an integer underflow before authentication. This is only exploitable if the client connects to a malicious SSH server.
Workaround
This vulnerability can be mitigated by configuring applications using the library to explicitly exclude AES-GCM from their preferred cipher lists.