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VaultwardenApplication · Dani Garcia

CVE-2026-43914

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-11
Fix available
A fix is available. Upgrade to 1.35.4 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Vaultwarden versions prior to 1.35.4 contain a security flaw where the unprotected /api/two-factor/send-email-login endpoint can be abused as an oracle to brute-force user passwords. When email 2FA is enabled on the server, this endpoint reveals whether username-password pairs are valid without applying any rate-limiting, allowing attackers to compromise accounts even for users who have not configured email 2FA.

MitigationUpgrade Vaultwarden to version 1.35.4 or later to patch the vulnerability. After upgrading, verify that rate-limiting is properly enforced on the affected endpoint.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
VaultwardenApplication
Affected:< 1.35.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify your Vaultwarden version
    Locate and inspect your running Vaultwarden instance version, typically visible in the admin panel, container logs, or by querying the /api/version endpoint if exposed
    Affected if Your installed version is lower than 1.35.4
  2. Verify if email 2FA is enabled on the server
    Access Vaultwarden admin settings or inspect the configuration file (usually vaultwarden.toml or environment variables) to determine whether the email two-factor authentication method is enabled globally
    Affected if Email 2FA is enabled on the server (this is a prerequisite for the vulnerability to apply)
  3. Inspect rate-limiting configuration for the affected endpoint
    Review your Vaultwarden rate-limiting settings, either in the admin panel configuration or in the configuration file, to verify whether any rate limits are applied to the /api/two-factor/send-email-login endpoint
    Affected if No rate-limiting is configured or enforced on the send-email-login endpoint

Your environment is affected if you run Vaultwarden version below 1.35.4 with email 2FA enabled and no rate-limiting on the send-email-login endpoint.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.35.4 or later
Fixed in 1.35.4
Vendor patch github.com →
Interim mitigation

Upgrade Vaultwarden to version 1.35.4 or later to patch the vulnerability. After upgrading, verify that rate-limiting is properly enforced on the affected endpoint.

Recommended fix High confidence

1.35.4

  1. 1. Stop the running Vaultwarden container: docker stop vaultwarden
  2. 2. Create a backup of the Vaultwarden data volume to ensure data safety
  3. 3. Pull the fixed Vaultwarden image with version 1.35.4: docker pull vaultwarden/server:1.35.4
  4. 4. Remove the old container: docker rm vaultwarden
  5. 5. Start a new container with the updated image using your existing configuration and volume mounts
  6. 6. Verify the container is running: docker ps | grep vaultwarden
  7. 7. Confirm the version is 1.35.4 by checking the admin interface or logs
Caveat None documented in the advisory; upgrade is recommended to address the critical authentication bypass

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Vaultwarden Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,920
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-43914 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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