Zitadel allows brute-forcing authentication factors

Summary

A vulnerability in Zitadel allowed brute-force attack on OTP, TOTP and password allowing to impersonate the attacked user.

Impact

An attacker can perform an online brute-force attack on OTP, TOTP, and passwords. While Zitadel allows preventing online brute force attacks in scenarios like TOTP, Email OTP, or passwords using a lockout mechanism. The mechanism is not enabled by default and can cause a denial of service for the corresponding user if enabled. Additionally, the mitigation strategies were not fully implemented in the more recent resource-based APIs.

Affected Versions

All versions within the following ranges, including release candidates (RCs), are affected:

• 4.x: 4.0.0 to 4.4.0 (including RC versions)
• 3.x: 3.0.0 to 3.4.2 (including RC versions)
• 2.x: v2.0.0 to 2.71.17

Patches

The vulnerability has been addressed in the latest releases. The patch resolves the issue by enforcing the lockout policy on all OTP, TOTP and password checks. Additionally a “tar pit” has been introduced to slow down brute-force attacks by default. Zitadel responses will be delayed by t seconds, where t increases over the number of failed attempts within a given timeframe.

4.x: Upgrade to >=4.6.0 3.x: Update to >=3.4.3 2.x: Update to >=2.71.18

Workarounds

The recommended solution is to update Zitadel to a patched version.

The problem might be mitigated by enabling the optional logout policy ("Password maximum attempts") or by implementing more strict rate limits.

Questions

If you have any questions or comments about this advisory, please email us at [email protected]

Credits

This vulnerability was found by zentrust partners GmbH during a scheduled penetration test. Thank you to the analysts Martin Tschirsich, Joud Zakharia, Christopher Baumann. The full report will be made public after the complete review.