Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Libexpat Project | Libexpat | <= 2.8.3 |
Related Weaknesses (CWE)
References
- https://github.com/libexpat/libexpat/pull/1321ExploitPatchVendor Advisory
- https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadrExploitPatchThird Party Advisory
FAQ
What is CVE-2026-66046?
CVE-2026-66046 is a vulnerability with a CVSS score of 7.5 (HIGH). 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-no...
How severe is CVE-2026-66046?
CVE-2026-66046 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-66046?
Check the references section above for vendor advisories and patch information. Affected products include: Libexpat Project Libexpat.