VULNERABILITY INTELLIGENCE

CVE-2026-66046

CVSS score7.5 HIGH
EPSS probability0.74%
CISA KEVNot currently listed
Published2026-08-18
Last modified2026-10-22
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

Weakness classification

  • disclosure@vulncheck.com: CWE-407

Primary references