Libssh: libssh: denial of service via zero-length input in ssh_get_hexa() (CVE-2026-0966)
Published Last modified Sources: Debian LTS, Red Hat, Debian, CVE.org, EUVD, Msrc Update Guide, BSI
What is affected, what to do
A flaw was found in libssh. The API function `ssh_get_hexa()` is vulnerable to a denial of service when processing zero-length input.
Update Red Hat Enterprise Linux 10 to version 0:0.12.0-2.el10, Red Hat Enterprise Linux 9 to version 0:0.10.4-18.el9, Red Hat Hardened Images to version 0.12.0-1.1.hum1.
- Affected
- Red Hat Enterprise Linux 10
lt *..0:0.12.0-2.el10 - Red Hat Enterprise Linux 9
lt *..0:0.10.4-18.el9 - Red Hat Hardened Images
lt *..0.12.0-1.1.hum1
- Red Hat Enterprise Linux 10
- Fixed in
- Red Hat Enterprise Linux 10
0:0.12.0-2.el10 - Red Hat Enterprise Linux 9
0:0.10.4-18.el9 - Red Hat Hardened Images
0.12.0-1.1.hum1
- Red Hat Enterprise Linux 10
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Metrics
8.2
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
6.5
CVSS v3
Severity Medium on the scale from 0 to 10.
Source: Debian LTS, Red Hat, Debian, CVE.org, EUVD, Msrc Update Guide, BSI
0.6 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 48.8
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 67.10 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 8.2 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 6.5
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.6 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 48.8
- High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-124
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
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.
Source: Debian LTS Advisories, redhat_csaf, Debian Security Advisories, cvelistv5, NVD (NIST), CVE.org (MITRE), ENISA EUVD, Microsoft Security Update Guide, BSI WID Portal, BSI CSAF
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Red Hat | Red Hat Enterprise Linux 10 |
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| Red Hat | Red Hat Enterprise Linux 6 |
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| Red Hat | Red Hat Enterprise Linux 7 |
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| Red Hat | Red Hat Enterprise Linux 8 |
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| Red Hat | Red Hat Enterprise Linux 9 |
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| Red Hat | Red Hat Hardened Images |
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| Red Hat | Red Hat OpenShift Container Platform 4 |
|
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| libssh | libssh |
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| redhat | hardened_images |
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| redhat | openshift_container_platform |
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Vendors and products
- Debian Libssh
- Libssh Libssh
- Red Hat Red Hat Enterprise Linux 10
- Red Hat Red Hat Enterprise Linux 6
- Red Hat Red Hat Enterprise Linux 7
- Red Hat Red Hat Enterprise Linux 8
- Red Hat Red Hat Enterprise Linux 9
- Red Hat Red Hat Hardened Images
- Red Hat Red Hat Openshift Container Platform 4
- Red Hat Redhat Enterprise Linux
- Red Hat Hardened Images
- Red Hat Openshift
Affected operating systems
| Linux | redhat | enterprise_linux | 10.0 |
| Linux | redhat | enterprise_linux | 8.0 |
| Linux | redhat | enterprise_linux | 9.0 |
| Linux | debian | libssh | bookworm |
| Linux | debian | libssh | trixie |
Weakness classes (CWE)
CWE-124Buffer Underwrite ('Buffer Underflow')
Base
The product writes to a buffer using an index or pointer that references a memory location prior to the beginning of the buffer.
Entry at MITRE CWE-124
References & sources
- access.redhat.comRHSA-2026:18160Vendor advisory, x_refsource_REDHAT
- access.redhat.comRHSA-2026:18683Vendor advisory, x_refsource_REDHAT
- access.redhat.comRHSA-2026:7067Vendor advisory, x_refsource_REDHAT
- access.redhat.comsecurity/cve/CVE-2026-0966Vulnerability database, x_refsource_REDHAT
- bugzilla.redhat.comRHBZ#2433121Issue tracking, x_refsource_REDHAT
- libssh.org2026/02/10/libssh-0-12-0-and-0-11-4-security-releases
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedRed Hat
Show 17 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/0xxx/CVE-2026-0966.json">CVE-2026-0966</a>Reference added —https://access.redhat.com/errata/RHSA-2026:18160Reference added —https://access.redhat.com/errata/RHSA-2026:18683Reference added —https://access.redhat.com/errata/RHSA-2026:7067Reference added —https://access.redhat.com/security/cve/CVE-2026-0966Reference added —https://bugzilla.redhat.com/show_bug.cgi?id=2433121Reference added —https://www.libssh.org/2026/02/10/libssh-0-12-0-and-0-11-4-security-releases/Reference removed https://access.redhat.com/errata/RHSA-2026:18160—Reference removed https://access.redhat.com/errata/RHSA-2026:18683—Reference removed https://access.redhat.com/errata/RHSA-2026:7067—Reference removed https://access.redhat.com/security/cve/CVE-2026-0966—Reference removed https://bugzilla.redhat.com/show_bug.cgi?id=2433121—Reference removed https://www.libssh.org/2026/02/10/libssh-0-12-0-and-0-11-4-security-releases/—Reference type removed https://access.redhat.com/errata/RHSA-2026:7067 Types: Vendor Advisory—Reference type removed https://access.redhat.com/security/cve/CVE-2026-0966 Types: Mitigation, Vendor Advisory—Reference type removed https://bugzilla.redhat.com/show_bug.cgi?id=2433121 Types: Issue Tracking, Vendor Advisory—Reference type removed https://www.libssh.org/2026/02/10/libssh-0-12-0-and-0-11-4-security-releases/ Types: Release Notes—Source identifier: secalert@redhat.com
Record modifiedRed Hat
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) changed Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 9 (+6)Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 9 (+6)Source identifier: secalert@redhat.com
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-0966"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-0966.svg?lang=en" alt="CVE-2026-0966 – NEOSEC Intel" height="20"></a>