Algorithmic Complexity Affecting expat package, versions *


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.68% (50th percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-EXPAT-18968951
  • published20 Aug 2026
  • disclosed18 Aug 2026

Introduced: 18 Aug 2026

NewCVE-2026-66046  (opens in a new tab)
CWE-407  (opens in a new tab)

How to fix?

There is no fixed version for Debian:unstable expat.

NVD Description

Note: Versions mentioned in the description apply only to the upstream expat package and not the expat package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1