Libssh: libssh: denial of service via zero-length input in ssh_get_hexa()
Summary
| CVE | CVE-2026-0966 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-03-26 21:17:00 UTC |
| Updated | 2026-05-11 17:16:11 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v3.1 8.2 HIGH from [email protected]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
EPSS: 0.000520000 probability, percentile 0.161450000 (date 2026-05-12)
Problem Types: CWE-124 | CWE-124 Buffer Underwrite ('Buffer Underflow')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 8.2 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H |
| 3.0 | [email protected] | Secondary | 6.5 | MEDIUM | CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H |
| 3.0 | CNA | CVSS | 6.5 | MEDIUM | CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
CVSS v3.0 Breakdown
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Libssh | Libssh | All | All | All | All |
| Operating System | Redhat | Enterprise Linux | 10.0 | All | All | All |
| Operating System | Redhat | Enterprise Linux | 8.0 | All | All | All |
| Operating System | Redhat | Enterprise Linux | 9.0 | All | All | All |
| Application | Redhat | Hardened Images | - | All | All | All |
| Application | Redhat | Openshift Container Platform | 4.0 | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Red Hat | Red Hat Hardened Images | unaffected 0.12.0-1.1.hum1 * rpm | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 10 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 6 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 7 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 8 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 9 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Hardened Images | Not specified | Not specified |
| CNA | Red Hat | Red Hat OpenShift Container Platform 4 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/security/cve/CVE-2026-0966 | [email protected] | access.redhat.com | Mitigation, Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:7067 | [email protected] | access.redhat.com | Vendor Advisory |
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | Issue Tracking, Vendor Advisory |
| www.libssh.org/2026/02/10/libssh-0-12-0-and-0-11-4-security-releases | [email protected] | www.libssh.org | Release Notes |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank Jakub Jelen (libssh), Jun Xu, Kang Yang, and Yunhang Zhang for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-01-26T23:14:46.617Z | Reported to Red Hat. |
| CNA | 2026-02-10T18:47:15.531Z | Made public. |
Workarounds
CNA: To mitigate this issue, consider disabling GSSAPI authentication if it is not required, or reduce the `LogLevel` in the `sshd_config` file to a value lower than `SSH_LOG_PACKET` (e.g., `INFO`). To disable GSSAPI authentication, add or modify the following line in `/etc/ssh/sshd_config`: `GSSAPIAuthentication no` To reduce logging verbosity, add or modify the following line in `/etc/ssh/sshd_config`: `LogLevel INFO` After making changes to `sshd_config`, the `sshd` service must be restarted for the changes to take effect. This may temporarily interrupt active SSH sessions.