CVE-2025-5987: Libssh: invalid return code for chacha20 poly1305 with openssl backend

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-07-07 · updated 2026-10-16
Weakness: CWE-393

Description

A flaw was found in libssh when using the ChaCha20 cipher with the OpenSSL library. If an attacker manages to exhaust the heap space, this error is not detected and may lead to libssh using a partially initialized cipher context. This occurs because the OpenSSL error code returned aliases with the SSH_OK code, resulting in libssh not properly detecting the error returned by the OpenSSL library. This issue can lead to undefined behavior, including compromised data confidentiality and integrity or crashes.

Affected products

libssh: from 0.10.0 before 0.11.2 — fixed in 0.11.2

How to fix

Upgrade to a fixed version: libssh 0.11.2. Check the vendor advisory for mitigations.

References

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