CVE-2026-86140: In libxml2 before 2.15.4, xmlSnprintfElements in valid.c has a strcat stack-based buffer overflow.

Q: How do I fix CVE-2026-86140?

libxml2: upgrade to 2.15.4. Exact commands for each OS are on this page.

Q: Is CVE-2026-86140 being exploited?

CVE-2026-86140 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-2026-86140 affect?

CVE-2026-86140 affects libxml2. Severity is high (CVSS 8.0). In libxml2 before 2.15.4, xmlSnprintfElements in valid.c has a strcat stack-based buffer overflow.

Routine

HIGH 8.0UPGRADE

CVE-2026-86140 is a high-severity flaw (CVSS 8.0) affecting libxml2. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In libxml2 before 2.15.4, xmlSnprintfElements in valid.c has a strcat stack-based buffer overflow.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.0 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 95%)
CISA exploited list	No
Weakness	CWE-121
Published	2026-09-05
Last modified	2026-09-15

Publisher (CNA): MITRE · Vendor: xmlsoft

Last updated 2026-09-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-05 05:17 UTCPublished CVE record published
2026-09-15 19:39 UTCUpdated Record last modified

xmlsoft libxml2 UPGRADE

Affected: < 2.15.4

Fixed in: 2.15.4

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2.15.4 (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

Amazon Linux 2 ALAS: ALAS2-2026-3940 (medium): libxml2 2026-09-28

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-2026-86140?

libxml2: upgrade to 2.15.4. Exact commands for each OS are on this page.

Is CVE-2026-86140 being exploited?

CVE-2026-86140 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-2026-86140 affect?

CVE-2026-86140 affects libxml2. Severity is high (CVSS 8.0). In libxml2 before 2.15.4, xmlSnprintfElements in valid.c has a strcat stack-based buffer overflow.

How urgent is CVE-2026-86140?

Priority 29/100. High severity

Software pages

libxml2 vulnerabilities

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References

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