C14N Denial of Service

Attack surface: Canonicalization

Attack impact: Denial of service

Description: C14N can be an expensive operation, requiring complex processing (Boyer ‟01), including entity expansion and normalization of whitespace, namespace declarations, and coalescing of adjacent text and CDATA nodes. This requires building a DOM and performing memory- and processor-intensive operations.

Exploit scenario: Attacker replaces the SignedInfo or XML content identified by a Reference with a very large set of XML data containing many namespace declarations, redundant adjacent text nodes, etc., leading to a denial of service condition.

Mitigation: Limit the total size of XML submitted for canonicalization.

Applies to XML Encryption? No

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