CVE-2026-86143: In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback and xmlBufUse causes negative lengths to reach write callbacks, aka a lack of a check for integer overflow before calling writecallback. This has security relevance for many types of uses of that length value within a callback.

Overview

Severity

Medium (CVSS 6.9)

CVSS Vector

CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

Exploit Status

Not Exploited

Patch Tuesday

2026-Sep

Released

2026-09-06

Last Updated

2026-09-08

EPSS Score

0.12% (percentile: 2.0%)

Affected Products (1)

Other

• 21495-17084

Security Updates (1)

• Security Update

Revision History

• 2026-09-06: Information published.
• 2026-09-08: Information published.