Executive brief
Parse Server is an open-source backend framework used to power mobile and web applications. A vulnerability in its login system allows unauthorized individuals to determine if a specific username or email address exists in the database by measuring how long the server takes to respond. This could lead to the exposure of user lists, which can be used for targeted phishing or credential-guessing attacks.
Technical details
A timing side-channel vulnerability (CWE-208) exists in the Parse Server login endpoint. The server's response time varies significantly depending on whether a user exists: if a user is found, the server performs a computationally expensive bcrypt password comparison; if the user does not exist, it returns a response immediately. This discrepancy allows an unauthenticated attacker to perform username enumeration via network-based timing analysis. The issue has been addressed in versions 8.6.74 and 9.8.0-alpha.6 by implementing a dummy bcrypt comparison when a user is not found, thereby normalizing response times.
Affected products
- Parse Community parse-server >= 9.0.0, < 9.8.0-alpha.6; < 8.6.74
Timeline
- 2026-04-05: disclosed: Initial disclosure by mtrezza
- 2026-04-07: advisory: NVD publication
- 2026-04-08: advisory: GitHub Advisory published