CVE-2021-42097

GNU Mailman before 2.1.35 may allow remote Privilege Escalation. A csrf_token value is not specific to a single user account. An attacker can obtain a value within the context of an unprivileged user account, and then use that value in a CSRF attack against an admin (e.g., for account takeover).

Weakness

The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.

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 [REF-1482].
• 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://www.openwall.com/lists/oss-security/2021/10/21/4
• https://bugs.launchpad.net/mailman/+bug/1947640
• https://mail.python.org/archives/list/mailman-announce%40python.org/thread/IKCO6JU755AP5G5TKMBJL6IEZQTTNPDQ/
• https://www.debian.org/security/2021/dsa-4991
• http://www.openwall.com/lists/oss-security/2021/10/21/4
• https://bugs.launchpad.net/mailman/+bug/1947640
• https://mail.python.org/archives/list/mailman-announce%40python.org/thread/IKCO6JU755AP5G5TKMBJL6IEZQTTNPDQ/
• https://www.debian.org/security/2021/dsa-4991