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CVE-2023-40021
Date: August 16, 2023
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 user's 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 user's 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.
Language: Python
Severity Score
Related Resources (6)
Severity Score
CVSS v3.1
Base Score: |
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Attack Vector (AV): | NETWORK |
Attack Complexity (AC): | HIGH |
Privileges Required (PR): | NONE |
User Interaction (UI): | REQUIRED |
Scope (S): | UNCHANGED |
Confidentiality (C): | NONE |
Integrity (I): | HIGH |
Availability (A): | NONE |