# CVE-2026-0966: Libssh: libssh: denial of service via zero-length input in ssh_get_hexa()

Status: published. Published: 2026-03-26. Updated: 2026-11-02.

A flaw was found in libssh. The API function `ssh_get_hexa()` is vulnerable to a denial of service when processing zero-length input. This can be exploited remotely by an attacker during GSSAPI (Generic Security Service Application Program Interface) authentication if the server's logging verbosity is set to `SSH_LOG_PACKET (3)` or higher. Successful exploitation could lead to a self-Denial of Service of the per-connection daemon process.

## Remediation

- workaround: Applications using libssh should avoid passing zero-length input to ssh_get_hexa(), ssh_get_fingerprint_hash(), and ssh_print_hexa().

For the remotely reachable GSSAPI authentication path, disable GSSAPI authentication in the affected libssh-based application if it is not required, or configure that application's libssh logging verbosity below SSH_LOG_PACKET (3). These measures address the GSSAPI logging path; they do not prevent other callers from passing zero-length input to the affected functions.

Configuration and any required restart depend on the application using libssh. Changing the host's OpenSSH sshd_config or restarting the OpenSSH sshd service is not a general mitigation for applications using libssh.

Apply the relevant vendor update containing the fix. Upstream fixed this issue in libssh 0.11.4 and 0.12.0; distribution packages may include a backported fix. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (libssh): ≥ 0:0.12.0-2.el10; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (libssh): ≥ 0:0.10.4-18.el9; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Hardened Images (libssh-main): ≥ 0.12.0-1.1.hum1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (libssh2): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (libssh2): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (libssh): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Hardened Images (libssh2): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-8): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.0: 6.5 (medium); CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 0.60% as of 2026-11-02; percentile 48.92%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-124

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/errata/RHSA-2026:18160 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:18683 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:7067 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-0966 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2433121 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://www.libssh.org/2026/02/10/libssh-0-12-0-and-0-11-4-security-releases/ (CNA: redhat)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-0966; retrieved 2026-11-02; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-0966; retrieved 2026-11-02; source updated Not reported

Revision: 033ef61262c06d3bfbb515ef072dde658759950228789b84c46e021f90dc41ba

Canonical: https://y2.dev/cve/CVE-2026-0966

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