Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:HSummary
CVE-2026-0966 is a high-severity Buffer Underflow (CWE-124) vulnerability in Redhat Enterprise Linux. Its CVSS base score is 8.2 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 45th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-0966 is a vulnerability in the libssh library's API function `ssh_get_hexa()`, which suffers from a buffer underwrite (CWE-124) when provided with zero-length input. This issue affects internal usages of the function in `ssh_get_fingerprint_hash()` and the deprecated `ssh_print_hexa()`, both of which are vulnerable to the same input condition where length is supplied by the calling application. Additionally, `ssh_get_hexa()` is invoked in the GSSAPI code for logging Object Identifiers (OIDs) received from the server during GSSAPI authentication. The vulnerability carries a CVSS v3.1 base score of 8.2 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H).
A remote, unauthenticated attacker can exploit this vulnerability by triggering GSSAPI authentication on a vulnerable libssh server that has logging verbosity set to at least SSH_LOG_PACKET (level 3). This leads to a self-denial-of-service condition, crashing the per-connection daemon process due to the buffer underwrite. Exploitation requires no privileges or user interaction, with low attack complexity over the network, resulting in high availability impact from process termination and low integrity impact.
Mitigation is available through updated libssh releases, including versions 0.12.0 and 0.11.4, as detailed in the libssh security advisory. Red Hat has addressed the issue in errata RHSA-2026:7067, with further details on their CVE page and Bugzilla entry (ID 2433121). Security practitioners should upgrade affected libssh instances and review GSSAPI authentication configurations and logging levels to prevent exposure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16330
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.4.1
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and analysis can discover buffer underwrite flaws before deployment but does not stop their introduction.
Input validation can enforce bounds on indices or pointers before buffer writes, structurally stopping underwrite conditions.
Memory protection mechanisms limit the blast radius of an out-of-bounds write even if the coding flaw exists.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly prevent introduction of buffer underwrite flaws via coding standards, reviews, and testing.
Vulnerability identification processes can discover buffer underwrite issues but do not prevent their creation.
Patching removes instances of the weakness after discovery but does not address root-cause prevention in code.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development catches buffer-underflow defects before release.
Secure SDLC mandates input validation and bounds checking that directly prevent buffer underflow.
Application security requirements can specify buffer-size and pointer-safety rules.
Secure architecture and engineering principles require safe memory-handling patterns.
Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds checks.