Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-86143

CVE-2026-86143HIGH

xmlsoft libxml2 — In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback and xmlBufUse causes negative lengths to reach write callba…

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   L   L   L   N  U  H  H  L    7.3   .0019    8.2     —

AFFECTED
  Product  Versions     Fixed
  libxml2  unspecified  —

TIMELINE
  Sep 5   Reserved by mitre
  Sep 5   Published (CNA: mitre)
  Sep 15  EXPLOIT PUBLISHED — CVE-2026-86143 (xmlsoft libxml2). Public exploit reference added.
  Sep 15  RESCORED — CVE-2026-86143 (xmlsoft libxml2). CVSS 6.9 → 7.3 (NVD).

CWE-192 · CNA: mitre · CVSS v3.1 · 3 references · NVD status: Analyzed

Description

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.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
September 5, 2026	Reserved	Reserved by mitre
September 5, 2026	Published	Published (CNA: mitre)
September 15, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-86143 (xmlsoft libxml2). Public exploit reference added.
September 15, 2026	RESCORED	RESCORED — CVE-2026-86143 (xmlsoft libxml2). CVSS 6.9 → 7.3 (NVD).

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
xmlsoft	libxml2	—	—	—

Weaknesses

CWE-192

References (3)

https://github.com/GNOME/libxml2/commit/90f293ba74d28b1d570920382e707586f68ebf35 [Patch]
https://github.com/GNOME/libxml2/compare/v2.15.3...v2.15.4 [Release Notes]
https://gitlab.gnome.org/GNOME/libxml2/-/work_items/1111 [Exploit, Vendor Advisory]

Authoritative record: CVE-2026-86143 at cve.org

Vendors: xmlsoft

Weaknesses: CWE-192

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-86143 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.