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CVE-2026-86140 xmlsoft CVE debrief

CVE-2026-86140 is a HIGH-severity vulnerability in libxml2 before version 2.15.4, caused by a stack-based buffer overflow in xmlSnprintfElements in valid.c. The CVE record was published on 2026-09-05T05:17:12.877Z and was last modified on 2026-09-15T19:39:17.010Z. The NVD entry is currently Analyzed. Defenders responsible for libxml2 deployments should assess exposure and prioritize verification and patching. This includes developers, security teams, and IT personnel managing systems that use libxml2. The vulnerability has a CVSS score of 8 and a severity of HIGH. The CVE record and NVD entry provide details on the vulnerability, but do not provide information on exploitation or 3)

Vendor
xmlsoft
Product
libxml2
CVSS
HIGH 8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-05
Original CVE updated
2026-09-15
Advisory published
2026-09-05
Advisory updated
2026-09-15

Who should care

Defenders responsible for libxml2 deployments should assess exposure and prioritize verification and patching. This includes developers, security teams, and IT personnel managing systems that use libxml2.

Why it matters

CVE-2026-86140 is a HIGH-severity vulnerability in libxml2 before version 2.15.4, caused by a stack-based buffer overflow in xmlSnprintfElements in valid.c. Defenders should prioritize verifying and applying the patch, as well as checking for vulnerable versions of libxml2 in their inventory.

  • Verify and apply the patch to prevent potential buffer overflow attacks
  • Check inventory for vulnerable versions of libxml2 to prioritize remediation
  • Monitor for potential exploitation attempts to detect potential attacks

Technical summary

The vulnerability is caused by a stack-based buffer overflow in xmlSnprintfElements in valid.c. The CVE record and NVD entry provide details on the vulnerability, but do not provide information on exploitation or impact. The vulnerability has a CVSS score of 8 and a severity of HIGH.

Defensive priority

Defenders should prioritize verifying and applying the patch, as well as checking for vulnerable versions of libxml2 in their inventory.

Recommended defensive actions

  • Verify and apply the patch to update libxml2 to version 2.15.4 or later
  • Check inventory for vulnerable versions of libxml2
  • Monitor for potential exploitation attempts

Evidence notes

The vulnerability is caused by a stack-based buffer overflow in xmlSnprintfElements in valid.c. The CVE record and NVD entry provide details on the vulnerability, but do not provide information on exploitation or impact.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-86140 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-86140

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-86140 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-86140

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.