Cédric Bonhomme

In Vulnerability-Lookup 5.5.1 up to but not including 6.4.1, a signed-in user could make the server allocate memory far out of proportion to their input through a webhook notification's payload template. Each placeholder's format specifier was passed unchanged to Python's string formatting, which builds the padded result before its size can be checked. A template of a few dozen bytes, such as {"text": "{title:>999999999}"}, therefore produced a string of about 1 GB when the notification form test-rendered it on save, and repeating such fields multiplied the cost. Templates that passed the save check could also repeat placeholders such as {text} thousands of times; the notification daemon rebuilt those on every webhook delivery. Deeply nested templates raised an unhandled recursion error (HTTP 500). An attacker needs only an account, which the default configuration lets anyone create after e-mail confirmation. They could exhaust the memory of web workers or the notification daemon, causing a denial of service. Version 6.4.1 caps every number in a format specifier at 256, limits a rendered template to 1,000,000 characters both on save and at delivery, and rejects templates nested deeper than 32 levels.

The account recovery functionality contains a time-of-check-to-time-of-use (TOCTOU) race condition—a scenario where a system checks a condition and then uses the result, but the condition changes between the check and the use—during the consumption of single-use recovery tokens. This occurs because the system verifies the token nonce and clears it in separate database operations. Consequently, two concurrent HTTP requests using the same valid token can both pass verification, allowing an attacker with a valid token to overwrite a legitimate user's password. Additionally, the `/user/confirm account/<token>` endpoint allows setting empty or trivially short passwords because the view handler performs a manual equality comparison between password fields without invoking the form's validation logic, bypassing complexity and length constraints. The issue resides in the `User` model (`website/models/user.py`) and the view layer (`website/web/views/user.py`).