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-$5k2.90-

Summaryinfo

A vulnerability, which was classified as problematic, was found in libexpat up to 2.8.1. This issue affects some unknown processing. Executing a manipulation can lead to integer overflow. This vulnerability is registered as CVE-2026-56405. The attack needs to be launched locally. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in libexpat up to 2.8.1 and classified as problematic. This vulnerability affects some unknown functionality. 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. CVE summarizes:

libexpat before 2.8.2 has an integer overflow in getAttributeId.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-56405 since 06/21/2026. The exploitation appears 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 321887 (Linux Distros Unpatched Vulnerability : CVE-2026-56405), 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 (321887), EUVD (EUVD-2026-38182) and CERT Bund (WID-SEC-2026-2025). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

  • Open Source expat

Productinfo

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.7
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

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

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-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Nessus ID: 321887
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-56405

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-2026-56405 (🔒)
GCVE (CVE): GCVE-0-2026-56405
GCVE (VulDB): GCVE-100-372640
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

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Do you need the next level of professionalism?

Upgrade your account now!