CVE-2026-59847: Libssh: libssh: integrity downgrade via openssl aes-gcm tag verification
Incorrect AES-GCM verification can allow traffic modification by an intermediary.
CVE published 2026-07-21 · Record updated 2026-09-01 · Snapshot checked 24 October 2026
Why this matters
Incorrect AES-GCM verification can allow traffic modification by an intermediary.
CVSS 3.1: 5.9 (MEDIUM). Source: CVE assigning authority.
A severity score describes the vulnerability, not the probability that your own website has been compromised. Exposure depends on the installed version, configuration and reachable code path.
When to check your system
Affected libssh builds using the OpenSSL backend on the Ubuntu releases in the advisory.
How to address it
Apply the vendor’s libssh security update and reload affected applications.
Record the installed package and vendor build, check the advisory’s prerequisites, back up, apply the vendor fix and test the affected site functions. Distribution packages may include backported fixes without changing the upstream version number.
Sources
This page summarises a selected advisory. It is not evidence that a particular website is vulnerable. Where an advisory covers several CVEs, check the linked record for this CVE’s exact affected range.