dani-garcia vaultwarden up to 1.35.3 API Endpoint send-email-login send_email_login excessive authentication

Summaryinfo

A vulnerability classified as problematic has been found in dani-garcia vaultwarden up to 1.35.3. Affected by this vulnerability is the function send_email_login of the file /api/two-factor/send-email-login of the component API Endpoint Handler. The manipulation leads to excessive authentication. This vulnerability is traded as CVE-2026-43914. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in dani-garcia vaultwarden up to 1.35.3. It has been rated as problematic. This issue affects the function send_email_login of the file /api/two-factor/send-email-login of the component API Endpoint Handler. The manipulation with an unknown input leads to a excessive authentication vulnerability. Using CWE to declare the problem leads to CWE-307. The product does not implement sufficient measures to prevent multiple failed authentication attempts within a short time frame, making it more susceptible to brute force attacks. Impacted is confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-43914 since 05/04/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1110.001 according to MITRE ATT&CK.

Upgrading to version 1.35.4 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-1285). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Open Source Vaultwarden

Productinfo

Vendor

• dani-garcia

Name

• vaultwarden

Version

• 1.35.0
• 1.35.1
• 1.35.2
• 1.35.3

Website

• Product: https://github.com/dani-garcia/vaultwarden/

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Entryinfo

Be aware that VulDB is the high quality source for vulnerability data.

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