CVE-2026-66046
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
Summary
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.
Affected Software
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| libexpat project | libexpat | 0 <= 2.8.3 | affected |
Weaknesses
- CWE-407: Inefficient Algorithmic Complexity
References
- https://github.com/libexpat/libexpat/pull/1321
- https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadratic-complexity
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