CVE-2026-86139: In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow.

Q: How do I fix CVE-2026-86139?

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

Q: Is CVE-2026-86139 being exploited?

CVE-2026-86139 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-2026-86139 affect?

CVE-2026-86139 affects libxml2. Severity is medium (CVSS 6.9). In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow.

Q: How urgent is CVE-2026-86139?

Priority 26/100. No elevated risk signals yet.

Routine

MEDIUM 6.9UPGRADE

CVE-2026-86139 is a medium-severity flaw (CVSS 6.9) 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, xmlURIEscapeStr in uri.c has an integer overflow.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.9 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 94%)
CISA exploited list	No
Weakness	CWE-190
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.

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-2026-86139?

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

Is CVE-2026-86139 being exploited?

CVE-2026-86139 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-2026-86139 affect?

CVE-2026-86139 affects libxml2. Severity is medium (CVSS 6.9). In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow.

How urgent is CVE-2026-86139?

Priority 26/100. No elevated risk signals yet.

Software pages

libxml2 vulnerabilities

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References

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