xmlsoft libxml2 up to 2.15.3 xmlIO xmlOutputWriteCallback integer overflow

Summaryinfo

A vulnerability, which was classified as problematic, has been found in xmlsoft libxml2 up to 2.15.3. Affected is the function xmlOutputWriteCallback of the component xmlIO. This manipulation causes integer overflow. This vulnerability is handled as CVE-2026-86143. It is possible to launch the attack on the local host. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in xmlsoft libxml2 up to 2.15.3. It has been declared as problematic. Affected by this vulnerability is the function xmlOutputWriteCallback of the component xmlIO. The manipulation with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-86143 since 09/05/2026. The exploitation appears to be easy. Attacking locally is a requirement. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 343104 (Linux Distros Unpatched Vulnerability : CVE-2026-86143), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.15.4 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (343104). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Document Processing Software

Vendor

• xmlsoft

Name

• libxml2

Version

• 2.15.0
• 2.15.1
• 2.15.2
• 2.15.3

License

• open-source

CPE 2.3info

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CPE 2.2info

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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