CVE-2026-11979: libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --she

Q: How do I fix CVE-2026-11979?

libxml2: upgrade to newer than 2.15.3. Exact commands for each OS are on this page.

Q: Is CVE-2026-11979 being exploited?

CVE-2026-11979 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-11979 affect?

CVE-2026-11979 affects libxml2. Severity is high (CVSS 7.8). 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

Routine

HIGH 7.8UPGRADE

CVE-2026-11979 is a high-severity flaw (CVSS 7.8) affecting libxml2. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 90%)
CISA exploited list	No
Weakness	CWE-121
Published	2026-06-29
Last modified	2026-10-25

Publisher (CNA): CERT.PL · Vendor: xmlsoft

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-29 14:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

xmlsoft libxml2 UPGRADE

Affected: <= 2.15.3

Fixed in: newer than 2.15.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libxml2 || rpm -q libxml2 || libxml2 --version

2. UPGRADE to newer than 2.15.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libxml2

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libxml2

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Advisories and coverage

Official advisories

CERT Polska: Vulnerability in libxml2 software 2026-06-29

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-11979?

libxml2: upgrade to newer than 2.15.3. Exact commands for each OS are on this page.

Is CVE-2026-11979 being exploited?

CVE-2026-11979 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-11979 affect?

CVE-2026-11979 affects libxml2. Severity is high (CVSS 7.8). 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

How urgent is CVE-2026-11979?

Priority 30/100. High severity

Software pages

libxml2 vulnerabilities

Related CVEs

CVE-2026-6653 CRITICAL 9.8 UPGRADE Use After Free in libxml2's xmlParseInternalSubset from GNOME libxml2 version 2.9.11 to 2.11.0 allows a remote

References

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