CVE-2026-86139

In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow.

CVE-2026-86139 is fixed in 5 products on 1 platform, first by DEBIAN-CVE-2026-86139, released September 11, 2026. It is not reported as exploited. Patch Radar priority: High.

High

CVSS

7.8

Moderate

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0017

5th percentile

In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow.

Where it's fixed

Product	Fixed in	Fix	Released
Linux
libxml2 · Debian 14	2.15.4+dfsg-1	DEBIAN-CVE-2026-86139	Sep 11, 2026
libxml2-16 · Ubuntu 26.04.1 LTS (resolute)	2.15.2+dfsg-0.1ubuntu0.3	libxml2-16 2.15.2+dfsg-0.1ubuntu0.3	Sep 17, 2026
libxml2-source · Ubuntu 26.04.1 LTS (resolute)	2.15.2+dfsg-0.1ubuntu0.3	libxml2-source 2.15.2+dfsg-0.1ubuntu0.3	Sep 17, 2026
libxml2-utils · Ubuntu 26.04.1 LTS (resolute)	2.15.2+dfsg-0.1ubuntu0.3	libxml2-utils 2.15.2+dfsg-0.1ubuntu0.3	Sep 17, 2026
python3-libxml2 · Ubuntu 26.04.1 LTS (resolute)	2.15.2+dfsg-0.1ubuntu0.3	python3-libxml2 2.15.2+dfsg-0.1ubuntu0.3	Sep 17, 2026

Details

Published
September 4, 2026
Weakness
Integer Overflow or Wraparound
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-86139

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