VDB-372639 · CVE-2026-56404 · EUVD-2026-38181

libexpat up to 2.8.1 integer overflow

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.6	$0-$5k	0.92

Summaryinfo

A vulnerability, which was classified as problematic, has been found in libexpat up to 2.8.1. This vulnerability affects unknown code. Performing a manipulation results in integer overflow. This vulnerability is cataloged as CVE-2026-56404. The attack must be initiated from a local position. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in libexpat up to 2.8.1. This affects an unknown functionality. The manipulation with an unknown input leads to a integer overflow vulnerability. CWE is classifying the issue as 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. This is going to have an impact on confidentiality, integrity, and availability.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-56404 since 06/21/2026. The exploitability is told to be difficult. Attacking locally is a requirement. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 321891 (Linux Distros Unpatched Vulnerability : CVE-2026-56404), 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 (321891), EUVD (EUVD-2026-38181) and CERT Bund (WID-SEC-2026-2025). Be aware that VulDB is the high quality source for vulnerability data.

Affected

Open Source expat

Productinfo

Name

libexpat

Version

Website

Product: https://github.com/libexpat/libexpat/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.7
VulDB Meta Temp Score: 5.6

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

CNA Base Score: 6.9
CNA Vector (MITRE): 🔒

CVSSv2info

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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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: No

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

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 321891
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-56404

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-2026-56404 (🔒)
GCVE (CVE): GCVE-0-2026-56404
GCVE (VulDB): GCVE-100-372639
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 (61), 06/21/2026 20:25 (1), 06/22/2026 12:40 (2), 06/22/2026 12:52 (7)
Complete: 🔍
Cache ID: 216::103