libxml2: Integer Coercion Error
CVE-2026-86143 is a high-severity integer coercion error vulnerability in libxml2 from Xmlsoft, with a CVSS 3.1 base score of 7.3 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 2.15.4 as the first without the flaw, so updating libxml2 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.19% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update libxml2 to 2.15.4 or a later version.
- Read the advisory on gitlab.gnome.org for workarounds and exact fixed builds.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 6.9 | Medium | CNA (mitre.org) |
| CVSS 3.1 | 7.3 | High | NVD |
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Integer Coercion Error
Integer coercion refers to a set of flaws pertaining to the type casting, extension, or truncation of primitive data types.
How developers prevent this class of flaw
- A language which throws exceptions on ambiguous data casts might be chosen.
- Design objects and program flow such that multiple or complex casts are unnecessary
- Ensure that any data type casting that you must use is entirely understood in order to reduce the plausibility of error in use.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Other vulnerabilities in libxml2
- 7.8 High severity
- 7.8 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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