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XXE

Description​

External entities is an element of XML documents, and attackers may replace the entity value with malicious data, alternate referrals, or compromise the security of the data the server/XML application has access to. Attackers may also use External Entities to have the web services download malicious code or content on the server for use in secondary or follow up attacks.

Remediation​

To safely prevent XXE attacks, always disable DTDs (External Entities) completely. Depending on the parser, the method should be similar to the following:

factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);

Disabling DTDs also helps secure the parser against Denial of Services attacks such as Billion Laughs.

If it is not possible to disable DTDs completely, disable external entities and external document type declarations in the way that's specific to each parser.

Configuration​

CheckId: injection/xxe

Examples​

Ignoring this check​

{
    "checks": {
        "injection/xxe": {
            "skip": true
        }
    }
}

Score​

  • Escape Severity: HIGH
  • OWASP: A08:2019
  • PCI DSS: _6_5_1
  • CWE
    • 610
    • 611
  • WASC: 43

CVSS​

  • CVSS_VECTOR: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L/E:F/RL:O/RC:C
  • CVSS_SCORE: 6.8

References​

http://projects.webappsec.org/XML-External-Entities