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CVE-2026-11979 — libxml2

CVE-2026-11979 is a CWE-121 vulnerability. A fix is available — see the affected versions and patch details below.

Stack-Based Buffer Overflow in libxml2

Published
Updated
Affected
1 product
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-11979.

EPSS Exploitation Probability

via FIRST.org ↗
0.1%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs4th percentile — riskier than 4% of all scored CVEsHighest risk
0.00%0.22%0.43%0.65%0.1%0.1%0.1%0.1%0.1%Jul 26Sep 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Description

libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size stack buffers without proper bounds checking. By supplying an overly long input line, an attacker can overflow internal buffers (command, arg, and argv) during input parsing. This results in memory corruption within the stack frame. Successful exploitation may cause a crash or potentially allow arbitrary code execution in the context of the xmlcatalog process.

This issue has been fixed in the commit c2e233fc.

NOTE: The maintainers of this project did not agree that this issue is a vulnerability and considered it a bug.

Affected Products

1 product · 1 configurations
Application
libxml2xmlsoft
≤ 2.15.3
range

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Fix

    Upgrade the affected component to the fixed release for CVE-2026-11979, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

  3. Workarounds

    Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This Moderate impact flaw in libxml2 affects the `xmlcatalog` utility when operating in `--shell` mode. Exploitation requires an attacker to provide specially crafted, excessively long input, leading to stack-based buffer overflows. This vulnerability is limited to scenarios where an attacker can control input to the…

Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Source: Red Hat security advisory for CVE-2026-11979 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Enterprise Linux 10libxml2-0:2.12.5-10.el10_2.3RHSA-2026:60394
Red Hat Enterprise Linux 8libxml2-0:2.9.7-21.el8_10.7RHSA-2026:61248
Red Hat Enterprise Linux 9libxml2-0:2.9.13-14.el9_8.4RHSA-2026:61247
Cert Manager support for Red Hat OpenShift release 1.20cert-manager/jetstack-cert-manager-rhel9:1790223279RHSA-2026:72394
Cert Manager support for Red Hat OpenShift release 1.20cert-manager/cert-manager-istio-csr-rhel9:1790223719RHSA-2026:72395
Cert Manager support for Red Hat OpenShift release 1.20cert-manager/cert-manager-operator-rhel9:1790272426RHSA-2026:72399
Cert Manager support for Red Hat OpenShift release 1.20cert-manager/jetstack-cert-manager-acmesolver-rhel9:1790589998RHSA-2026:72470
Cert Manager support for Red Hat OpenShift release 1.20cert-manager/cert-manager-istio-csr-rhel9:1790589914RHSA-2026:72475

Frequently Asked Questions

libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size stack buffers without proper bounds checking. By supplying an overly long input line, an attacker can overflow internal buffers (command, arg, and argv) during input parsing. This results in memory corruption within the stack frame. Successful exploitation may cause a crash or potentially allow arbitrary code execution in the context of the xmlcatalog process. This issue has been fixed in the commit c2e233fc. NOT
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CVE-2026-11979: libxml2: Stack-Based Buffer Overflow