CVE-2026-86137: In libxml2 before 2.15.4, xmlFAParsePosCharGroup has an out-of-bounds read, aka an out-of-bounds read in the NXT macro in xmlregexp.

lowCVSS 2.9CVE-2026-86137

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: low — CVSS 2.9
Published: 2026-09-08
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-86137

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-861370.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-86137	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for In libxml2

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

high[UPDATE] [hoch] libxml2: Mehrere Schwachstellen ermöglichen Denial of Servicecert-bund · 2026-09-10
high[NEU] [hoch] libxml2: Schwachstelle ermöglicht Denial of Servicecert-bund · 2026-09-09
highCVE-2026-74860: A flaw was found in libxml2 with Python bindings enabled. A remote attacker could exploit this…nvd · 2026-09-08
lowCVE-2026-86141: xmlregexp in libxml2 before 2.15.4 has a NULL pointer dereference in xmlRegNewParserCtxt after…msrc · 2026-09-08
mediumCVE-2026-86143: In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback and xmlBufUse ca…msrc · 2026-09-08
mediumCVE-2026-86139: In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow.msrc · 2026-09-08