Oppia is an online learning platform. When comparing a received CSRF token against the expected token, Oppia uses the string equality operator (==), which is not safe against timing attacks. By repeatedly submitting invalid tokens, an attacker can brute-force the expected CSRF token character by character. Once they have recovered the token, they can then submit a forged request on behalf of a logged-in user and execute privileged actions on that users behalf. In particular the function to validate received CSRF tokens is at oppia.core.controllers.base.CsrfTokenManager.is_csrf_token_valid. An attacker who can lure a logged-in Oppia user to a malicious website can perform any change on Oppia that the user is authorized to do, including changing profile information; creating, deleting, and changing explorations; etc. Note that the attacker cannot change a users login credentials. An attack would need to complete within 1 second because every second, the time used in computing the token changes. This issue has been addressed in commit b89bf80837 which has been included in release 3.3.2-hotfix-2. Users are advised to upgrade. There are no known workarounds for this vulnerability.
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Oppia | Oppia | 1.1.0 (including) | 3.3.2 (excluding) |
| Oppia | Oppia | 3.3.2 (including) | 3.3.2 (including) |