CWE-776Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

Description

The product uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.

If the DTD contains a large number of nested or recursive entities, this can lead to explosive growth of data when parsed, causing a denial of service.

Common consequences

• Availability→DoS: Resource Consumption (Other)
  If parsed, recursive entity references allow the attacker to expand data exponentially, quickly consuming all system resources.

Potential mitigations

• Operation
  If possible, prohibit the use of DTDs or use an XML parser that limits the expansion of recursive DTD entities.
• Implementation
  Before parsing XML files with associated DTDs, scan for recursive entity declarations and do not continue parsing potentially explosive content.

Related CWEs

Recent CVEs classified under this CWE