Executive brief
stoatchat is a chat application that secures user accounts through login credentials. An unauthenticated attacker can exploit error messages returned by the login endpoint to enumerate which email addresses are registered, defeating the application's account protection. While the attacker cannot access actual accounts or data, this information can be used to build lists of valid targets for subsequent attacks such as phishing or password spraying.
Technical details
The vulnerability stems from error responses that include source file location fields (file path, line number, column) that differ between code paths for registered versus unregistered accounts. Specifically, POST /api/auth/session/login returns 401 InvalidCredentials with different location fields depending on whether an account exists, allowing unauthenticated network attackers to distinguish between the two cases. The fix was to either normalize error locations or remove location information from client-facing responses, which is implemented in version 0.15.5.
Affected products
- stoatchat stoatchat before 0.15.5
Timeline
- 2026-09-26: disclosed
- 2026-09-26: patched: version 0.15.5 released