CVE-2026-43914: Vaultwarden brute-force protection bypass in email 2FA endpoint

CVE-2026-43914 · Severity: high · CVSS 7.3 · Published 2026-05-11

Vaultwarden, an open-source password management server, contains a flaw that allows attackers to bypass security measures designed to prevent repeated login attempts. By exploiting a specific email-based login feature, an attacker can rapidly test thousands of passwords against a user's account without being blocked. If successful, this could lead to unauthorized access to a user's entire vault of stored passwords and sensitive credentials.

Quick answers

Is CVE-2026-43914 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-43914 being exploited in the wild.
How severe is CVE-2026-43914?
High severity, with a CVSS score of 7.3, published 11 May 2026.
Which products and versions are affected?
Vaultwarden Vaultwarden < 1.35.4.
Is there a fix for CVE-2026-43914?
A patch was published on 2026-02-23: Fix merged in PR 6867 and released in version 1.35.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-43914 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-43914?
Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A brute-force protection bypass exists in Vaultwarden's 'send_email_login' function (located in email.rs) via the '/api/two-factor/send-email-login' endpoint. While standard login endpoints are protected by the 'check_limit_login' rate-limiting function, this specific 2FA endpoint was left unprotected. It acts as an authentication oracle: if a username/password combination is correct, it returns a 200 OK or a 'Two factor not found' message; if incorrect, it returns 'Username or password is incorrect'. This allows a network-based attacker to perform high-speed password guessing against any user on the server, regardless of whether that specific user has email 2FA enabled, provided the server itself has the email 2FA feature active. The issue is resolved in version 1.35.4 by implementing proper rate limiting on the affected endpoint.

Affected products

  • Vaultwarden Vaultwarden < 1.35.4

Timeline

  • 2026-02-23: patched: Fix merged in PR 6867 and released in version 1.35.4
  • 2026-04-25: advisory: GitHub Security Advisory published
  • 2026-05-11: disclosed: CVE published to NVD

References

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