Vulnerability in Xmlsoft Libxml2
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.9 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L.
EPSS exploit prediction
EPSS: 0.002 (8.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 8th percentile — 8.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.002 · change: +0.001
Affected products
Weakness classification (CWE)
References
- github.com/GNOME/libxml2/commit/90f293ba74d28b1d570920382e707586f68ebf35 (Patch)
- github.com/GNOME/libxml2/compare/v2.15.3...v2.15.4 (Release Notes)
- gitlab.gnome.org/GNOME/libxml2/-/work_items/1111 (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-86143?
- CVE-2026-86143 is a medium-severity vulnerability in Xmlsoft Libxml2, classified under CWE-192. CVSS score: 6.9/10. Published 2026-09-05.
- How severe is CVE-2026-86143?
- Medium severity. CVSS v3 base score is 6.9 out of 10.