5.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2023-52426

CVE-2023-52426: libexpat through 2.5.0 allows recursive XML Entity Expansion if XML_DTD is undefined at compile...

libexpat through 2.5.0 allows recursive XML Entity Expansion if XML_DTD is undefined at compile time.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2023-52426

CVE-2023-52426:

5.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

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Root Cause Analysis

The vulnerability (CVE-2023-52426) arises because libexpat's protection against recursive XML entity expansion (Billion Laughs attack) is conditionally compiled based on the XML_DTD preprocessor macro. If XML_DTD is undefined at compile time (and, before the analyzed patch, XML_GE was not 1), these crucial security features, including accounting for entity expansion and recursion depth, are omitted. The provided commit 0f075ec8ecb5e43f8fdca5182f8cca4703da0404 fixes this by broadening the condition to #if defined(XML_DTD) || XML_GE == 1. The identified functions are directly involved in parsing XML content, processing entity definitions, or expanding entities. In a vulnerable build (where XML_DTD is undefined), these functions would lack the necessary checks (like accountingDiffTolerated, entityTrackingOnOpen, entityTrackingOnClose), making them susceptible to the described attack. The patch evidence clearly shows these checks being guarded by the conditional compilation directives that were previously insufficient.

Vulnerable functions

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WAF Protection Rules

WAF Rule

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Reasoning

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