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OpenAdvisories
High ALAS2-2026-3965 1 CVE

Important: expat security update (Amazon Linux 2)

Published Oct 12, 2026 · Updated Oct 12, 2026

Summary

Package updates are available for Amazon Linux 2 that fix the following vulnerabilities: CVE-2026-66046: 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.

Fixed packages 4

ReleasePackageFixed in
Amazon Linux · 2 expat 0:2.1.0-15.amzn2.0.9
Amazon Linux · 2 expat-debuginfo 0:2.1.0-15.amzn2.0.9
Amazon Linux · 2 expat-devel 0:2.1.0-15.amzn2.0.9
Amazon Linux · 2 expat-static 0:2.1.0-15.amzn2.0.9

Vulnerabilities 1

  • High 7.5

    Expat Denial of Service via storeAtts() Quadratic Complexity

    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 elementTy…

References

  • web
    https://alas.aws.amazon.com/cve/html/CVE-2026-66046.html