CVE-2026-115506
Description
A flaw was found in expat. The parser's protection mechanism against recursive entity expansion detects amplification thresholds too late during document processing. A remote attacker can exploit this vulnerability by supplying a crafted XML document with nested entity definitions, causing excessive CPU consumption and resulting in a Denial of Service (DoS).
Statement
This vulnerability is rated as Important because remote, unauthenticated attackers can cause severe CPU exhaustion in applications processing untrusted XML data, leading to a denial of service without requiring user interaction. Red Hat Enterprise Linux ships expat as a foundational shared library used across numerous core packages, servers, and desktop runtimes. Exploitation succeeds when an exposed application processes maliciously structured documents featuring deeply nested entity definitions, overwhelming parsing routines before protective thresholds engage.
Mitigation
Restrict network access to services that parse untrusted XML to trusted clients only. Where possible, disable DTD / external entity processing in application XML parsers. Apply process CPU/memory limits.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| 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:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (Other)
If the DTD contains a large number of nested or recursive entities, this allows the attacker to expand data exponentially when the DTD is parsed, quickly consuming all system resources.
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