CVE-2014-5241

The JSONP endpoint in includes/api/ApiFormatJson.php in MediaWiki before 1.19.18, 1.20.x through 1.22.x before 1.22.9, and 1.23.x before 1.23.2 accepts certain long callback values and does not restrict the initial bytes of a JSONP response, which allows remote attackers to conduct cross-site request forgery (CSRF) attacks, and obtain sensitive information, via a crafted OBJECT element with SWF content consistent with a restricted character set.

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://advisories.mageia.org/MGASA-2014-0309.html
• http://openwall.com/lists/oss-security/2014/08/14/5
• http://secunia.com/advisories/59738
• http://www.debian.org/security/2014/dsa-3011
• http://www.mandriva.com/security/advisories?name=MDVSA-2014:153
• https://bugzilla.wikimedia.org/show_bug.cgi?id=68187
• https://lists.wikimedia.org/pipermail/mediawiki-announce/2014-July/000157.html