PatchTheCVECVE-2026-86143: In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback and xmlBufUse causes negative le
CVE-2026-86143 is a medium-severity flaw (CVSS 6.9) affecting libxml2. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
Why this priority
- Public exploit reference
A fixed release or distro patch exists.
Risk facts
| CVSS score | 6.9 (Medium) |
| Attack vector | Local |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.2% (top 91%) |
| CISA exploited list | No |
| Weakness | CWE-192 |
| Published | 2026-09-05 |
| Last modified | 2026-09-15 |
Last updated 2026-09-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-86143?
libxml2: upgrade to 2.15.4. Exact commands for each OS are on this page.
Is CVE-2026-86143 being exploited?
CVE-2026-86143 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-86143 affect?
CVE-2026-86143 affects libxml2. Severity is medium (CVSS 6.9). 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 relevan
How urgent is CVE-2026-86143?
Priority 31/100. Public exploit reference
Software pages
Related CVEs
- CVE-2026-6732 MEDIUM 6.5 UPGRADE MITIGATE A flaw was found in libxml2
- CVE-2026-6653 CRITICAL 9.8 UPGRADE Use After Free in libxml2's xmlParseInternalSubset from GNOME libxml2 version 2.9.11 to 2.11.0 allows a remote
- CVE-2026-11979 HIGH 7.8 UPGRADE libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --she
- CVE-2026-86137 LOW 2.9 UPGRADE In libxml2 before 2.15.4, xmlFAParsePosCharGroup has an out-of-bounds read, aka an out-of-bounds read in the N
- CVE-2026-86138 MEDIUM 6.9 UPGRADE In libxml2 before 2.15.4, xmlDictAddQString in dict.c has an integer overflow and resultant heap-based buffer