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Libxml2 CVE-2026-86143

| EUVDEUVD-2026-71822 HIGH
Integer Coercion Error (CWE-192)
2026-09-05 mitre GHSA-r2q6-6v35-773j
Buffer Overflow Libxml2
7.3
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
CWE-192
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 16, 2026

Integer-overflow handling in libxml2's xmlIO output path lets a negative length reach application-supplied write callbacks, allowing memory corruption or denial of service in programs that serialize large XML documents. All libxml2 builds before 2.15.4 are affected; the upstream commit 90f293ba adds INT_MAX guards to xmlOutputBufferWrite and xmlOutputBufferFlush and the fix ships in 2.15.4 (also distributed via RHSA-2026:64463). CVSS is 7.3 (AV:L/PR:L), EPSS is only 0.12% (2nd percentile), there is no public exploit identified at time of analysis, and the issue is not listed in CISA KEV.

Affected VersionsENISA

libxml2 0 <2.15.4

Affected Packages

euvd libxml2 fix: 2.15.4

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Vendor (mitre) PRIMARY MEDIUM
NVD 7.3 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
vuln.today AI 6.9 MEDIUM

AV:L and AC:H because INT_MAX-scale output buffers are impractical without local/controlled large documents; C:H/I:H reflect callback-level memory corruption; A:L for incidental crash risk.

3.1 AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
4.0 AV:L/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
SUSE 6.9 MEDIUM
AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
Red Hat 6.9 MEDIUM

Primary rating from Vendor (mitre).

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
Low

Lifecycle Timeline

5
Analysis Updated
Sep 15, 2026 - 19:42 vuln.today
v2 - CVSS changed
Severity Changed
Sep 15, 2026 - 19:37 NVD
MEDIUM HIGH
CVSS changed
Sep 15, 2026 - 19:37 NVD
6.9 (MEDIUM) 7.3 (HIGH)
Patch available
Sep 05, 2026 - 06:01 EUVD
CVE Published
Sep 05, 2026 - 04:31 cve.org
MEDIUM 6.9

DescriptionNVD

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.

Threat Intelligence Overview

EPSS Score
0.1%
Top 98% exploitable
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS MSRC Vendor GitHub VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.1%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
High

Priority Score

36
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +36
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

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Same weakness CWE-192 – Integer Coercion Error

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise Micro 5.3 Not-Affected
SUSE Linux Enterprise Micro 5.4 Not-Affected
SUSE Linux Enterprise Micro 5.5 Not-Affected

References

Advisories & patches
ADVISORY https://access.redhat.com/errata/RHSA-2026:64463 ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-86143 ADVISORY https://seclists.org/oss-sec/2026/q3/657 ADVISORY https://ubuntu.com/security/notices/USN-8910-1 ADVISORY https://vuldb.com/vuln/399211 REF https://github.com/GNOME/libxml2/commit/90f293ba74d28b1d570920382e707586f68ebf35 REF https://github.com/GNOME/libxml2/compare/v2.15.3...v2.15.4 REF https://gitlab.gnome.org/GNOME/libxml2/-/work_items/1111

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