CVE-2009-0499

Cross-site request forgery (CSRF) vulnerability in the forum code in Moodle 1.7 before 1.7.7, 1.8 before 1.8.8, and 1.9 before 1.9.4 allows remote attackers to delete unauthorized forum posts via a link or IMG tag to post.php.

Weakness

The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.

Affected Software

Potential Mitigations

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, use anti-CSRF packages such as the OWASP CSRFGuard. [REF-330]
• Another example is the ESAPI Session Management control, which includes a component for CSRF. [REF-45]
• Use the “double-submitted cookie” method as described by Felten and Zeller:
• When a user visits a site, the site should generate a pseudorandom value and set it as a cookie on the user’s machine. The site should require every form submission to include this value as a form value and also as a cookie value. When a POST request is sent to the site, the request should only be considered valid if the form value and the cookie value are the same.
• Because of the same-origin policy, an attacker cannot read or modify the value stored in the cookie. To successfully submit a form on behalf of the user, the attacker would have to correctly guess the pseudorandom value. If the pseudorandom value is cryptographically strong, this will be prohibitively difficult.
• This technique requires Javascript, so it may not work for browsers that have Javascript disabled. [REF-331]

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/111.html
• https://cwe.mitre.org/data/definitions/462.html
• https://cwe.mitre.org/data/definitions/467.html
• https://cwe.mitre.org/data/definitions/62.html

References

• http://cvs.moodle.org/moodle/mod/forum/post.php?r1=1.154.2.14\u0026r2=1.154.2.15
• http://lists.opensuse.org/opensuse-security-announce/2009-03/msg00004.html
• http://moodle.org/security/
• http://secunia.com/advisories/34418
• http://www.openwall.com/lists/oss-security/2009/02/04/1