CVE-2026-43914: Vaultwarden: Brute-force protection bypass vulnerability

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-11 · updated 2026-10-26
Weakness: CWE-307

Description

Vaultwarden is a Bitwarden-compatible server written in Rust. Prior to 1.35.4, there is a security vulnerability in Vaultwarden that allows bypassing the login brute-force protection if email 2fa is enabled. If email 2fa is enabled, the unprotected 2fa-function send_email_login (email.rs, api endpoint /api/two-factor/send-email-login) also acts as an oracle determining whether a username-password combination is correct. An attacker can abuse that endpoint to brute-force passwords without rate-limiting. This works even for users who don't have email 2fa configured. This vulnerability is fixed in 1.35.4.

Affected products

dani-garcia vaultwarden: before 1.35.4 — fixed in 1.35.4

How to fix

Upgrade to a fixed version: dani-garcia vaultwarden 1.35.4. Check the vendor advisory for mitigations.

References

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