libexpat up to 2.8.1 integer overflow

CVSS Meta Temp Score
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CTI Interest Score
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5.4$0-$5k4.61-

Summaryinfo

A vulnerability was found in libexpat up to 2.8.1. It has been declared as problematic. This affects an unknown function. Such manipulation leads to integer overflow. This vulnerability is traded as CVE-2026-56409. An attack has to be approached locally. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in libexpat up to 2.8.1. It has been rated as problematic. Affected by this issue is some unknown processing. The manipulation with an unknown input leads to a integer overflow vulnerability. Using CWE to declare the problem leads to 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. Impacted is confidentiality, integrity, and availability. CVE summarizes:

xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is used.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-56409 since 06/21/2026. The exploitation is known to be difficult. The attack needs to be approached locally. There are neither technical details nor an exploit publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 321889 (Linux Distros Unpatched Vulnerability : CVE-2026-56409), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.8.2 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (321889), EUVD (EUVD-2026-38186) and CERT Bund (WID-SEC-2026-2025). Once again VulDB remains the best source for vulnerability data.

Affected

  • Open Source expat

Productinfo

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 4.5
VulDB Temp Score: 4.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 6.5
CNA Vector (MITRE): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Integer overflow
CWE: CWE-190 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 321889
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-56409

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: libexpat 2.8.2
Patch: github.com

Timelineinfo

06/21/2026 Advisory disclosed
06/21/2026 +0 days CVE reserved
06/21/2026 +0 days VulDB entry created
06/22/2026 +1 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Confirmed

CVE: CVE-2026-56409 (🔒)
GCVE (CVE): GCVE-0-2026-56409
GCVE (VulDB): GCVE-100-372644
EUVD: 🔒
CERT Bund: WID-SEC-2026-2025 - libexpat: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Entryinfo

Created: 06/21/2026 19:18
Updated: 06/22/2026 12:52
Changes: 06/21/2026 19:18 (62), 06/21/2026 20:25 (1), 06/22/2026 12:40 (2), 06/22/2026 12:52 (7)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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