GnuPG version 2.1.12 - 2.2.11 contains a Cross ite Request Forgery (CSRF) vulnerability in dirmngr that can result in Attacker controlled CSRF, Information Disclosure, DoS. This attack appear to be exploitable via Victim must perform a WKD request, e.g. enter an email address in the composer window of Thunderbird/Enigmail. This vulnerability appears to have been fixed in after commit 4a4bb874f63741026bd26264c43bb32b1099f060.
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
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Gnupg | Gnupg | 2.1.12 (including) | 2.2.11 (including) |
| Red Hat Enterprise Linux 8 | RedHat | gnupg2-0:2.2.20-2.el8 | * |
| Gnupg2 | Ubuntu | bionic | * |
| Gnupg2 | Ubuntu | cosmic | * |
| Gnupg2 | Ubuntu | devel | * |
| Gnupg2 | Ubuntu | esm-infra/bionic | * |
| Gnupg2 | Ubuntu | upstream | * |
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
- https://sektioneins.de/en/advisories/advisory-012018-gnupg-wkd.html
- https://sektioneins.de/en/blog/18-11-23-gnupg-wkd.html
- https://usn.ubuntu.com/3853-1/
- https://sektioneins.de/en/advisories/advisory-012018-gnupg-wkd.html
- https://sektioneins.de/en/blog/18-11-23-gnupg-wkd.html
- https://usn.ubuntu.com/3853-1/