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Vulnerabilities CVE-2026-66046

CVE-2026-66046

High
Open
TLP:CLEAR

Expat Denial of Service via storeAtts() Quadratic Complexity

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Description

Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options.

Details

CVSS Score
8.7
CVSS Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Confidence
90%
Published
Aug 18, 2026
Last Modified
Aug 18, 2026
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