Observable response discrepancy in PostgreSQL SCRAM authentication allows an unauthenticated user to test the existence of a user via observing the SCRAM iteration count. This requires the probed user to have a non-default scram_iterations count, because the authentication challenge for a nonexistent user reports the default scram_iterations. Within major versions 16-18, minor versions before PostgreSQL 18.5, 17.11, and 16.15 are affected. Versions before PostgreSQL 16 are unaffected.
Weakness
The product provides different responses to incoming requests in a way that reveals internal state information to an unauthorized actor outside of the intended control sphere.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Postgresql-10 | Ubuntu | upstream | * |
| Postgresql-12 | Ubuntu | upstream | * |
| Postgresql-9.3 | Ubuntu | upstream | * |
| Postgresql-9.5 | Ubuntu | upstream | * |
Potential Mitigations
- Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
- Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
- Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success.
- If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files.
- Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/331.html
- https://cwe.mitre.org/data/definitions/332.html
- https://cwe.mitre.org/data/definitions/541.html
- https://cwe.mitre.org/data/definitions/580.html