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Advisories

Expat Denial of Service via storeAtts() Quadratic Complexity

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severity
high
date
Affecting

  • libexpat <= 2.8.3

CWE
  • CWE-407 Inefficient Algorithmic Complexity
CVSS
8.7
CVSS V4 Vector
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
References
Credit
Fabian Wahle (Hap Security), Sebastian Pipping, VulnCheck
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.

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