CVE-2026-66046
High · 7.5CVSS
7.5
EPSS
0.7%
Published
Aug 18, 2026
CISA due date
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The record
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 packages
| Ecosystem | Package | Introduced | Fixed |
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