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AES-GCM Integrity Verification Bypass in libssh OpenSSL Backend
CVE-2026-59847 is an integrity-verification vulnerability in libssh builds using the OpenSSL cryptographic backend. Incorrect AES-GCM finalization and authentication-tag verification checks can effectively disable integrity protection for affected SSH connections. An in-path attacker can modify encrypted traffic so that altered plaintext is accepted without detection. Specific vulnerable function names and upstream affected-version boundaries are not established.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation compromises the integrity of SSH communications by allowing attacker-modified data to be accepted without detection. The vulnerability is rated CVSS v3 7.5 with vector CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N, reflecting high integrity impact and no assessed confidentiality or availability impact. Code execution, privilege escalation, and plaintext disclosure are not established consequences of this vulnerability.
If you can’t patch tonight, do this now.
Until patched, avoid affected OpenSSL-backed libssh builds where feasible. Reduce opportunities for in-path manipulation by using trusted network paths, network segmentation, or an independently authenticated and encrypted transport layer. Network controls reduce exposure but do not correct the defective AES-GCM verification.
Patch, then assume compromise.
Install the vendor-provided security update for libssh. Fixed Ubuntu libssh-4 package versions are 0.11.3-1ubuntu2.1 for Ubuntu 26.04 LTS, 0.10.6-2ubuntu0.5 for Ubuntu 24.04 LTS, and 0.9.6-2ubuntu0.22.04.8 for Ubuntu 22.04 LTS. Debian trixie provides version 0.11.5-0+deb13u1. Echo provides version 0.12.0-3+e2 or later. On Amazon Linux 2023, apply advisory ALAS2023-2026-3096 using the supported package-update procedure. These are distribution-specific fixed versions, not universal upstream version boundaries.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
38 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.