CVE-2026-76956
Description
A flaw was found in libexpat. This vulnerability arises from the software misinterpreting a return code, leading to insufficient randomness (entropy) for hash functions. A remote attacker could exploit this by sending specially crafted XML content, triggering hash flooding attacks. This can result in a denial of service (DoS), making the affected system or application unavailable to legitimate users.
Statement
Red Hat ships libexpat (packaged as "expat") across many products. This vulnerability was introduced in libexpat 2.8.2. Most Red Hat products ship expat versions prior to 2.8.2 and are therefore not affected. Only products shipping expat 2.8.2 or 2.8.3 are vulnerable to this hash flooding denial of service.
Mitigation
There is no mitigation for this flaw other than updating to libexpat 2.8.4 or later.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.9 | N/A | 5.9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat CVSS v3 Score Explanation
Corrected AC:L to AC:H — vulnerability requires getentropy() as entropy source, a platform-specific build-time condition beyond attacker control. Aligns with CVEORG assessment.
Understanding the Weakness (CWE)
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
An attacker could guess the random numbers generated and could gain unauthorized access to a system if the random numbers are used for authentication and authorization.
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