An issue was discovered in the Security component in Symfony 2.7.x before 2.7.48, 2.8.x before 2.8.41, 3.3.x before 3.3.17, 3.4.x before 3.4.11, and 4.0.x before 4.0.11. By default, a users session is invalidated when the user is logged out. This behavior can be disabled through the invalidate_session option. In this case, CSRF tokens were not erased during logout which allowed for CSRF token fixation.
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
| Name |
Vendor |
Start Version |
End Version |
| Symfony |
Sensiolabs |
2.7.0 (including) |
2.7.48 (excluding) |
| Symfony |
Sensiolabs |
2.8.0 (including) |
2.8.41 (excluding) |
| Symfony |
Sensiolabs |
3.3.0 (including) |
3.3.17 (excluding) |
| Symfony |
Sensiolabs |
3.4.0 (including) |
3.4.11 (excluding) |
| Symfony |
Sensiolabs |
4.0.0 (including) |
4.0.11 (excluding) |
| Symfony |
Ubuntu |
artful |
* |
| Symfony |
Ubuntu |
bionic |
* |
| Symfony |
Ubuntu |
esm-apps/bionic |
* |
| Symfony |
Ubuntu |
esm-apps/xenial |
* |
| Symfony |
Ubuntu |
upstream |
* |
| Symfony |
Ubuntu |
xenial |
* |
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]
References