CVE-2026-27898
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 · uneditedVaultwarden is an unofficial Bitwarden compatible server written in Rust, formerly known as bitwarden_rs. Prior to version 1.35.4, an authenticated regular user can specify another user’s cipher_id and call "PUT /api/ciphers/{id}/partial" Even though the standard retrieval API correctly denies access to that cipher, the partial update endpoint returns 200 OK and exposes cipherDetails (including name, notes, data, secureNote, etc.). This issue has been patched in version 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 confidenceVaultwarden versions prior to 1.35.4 contain an Insecure Direct Object Reference (IDOR) vulnerability where an authenticated regular user can access and partially update another user's cipher by specifying that user's cipher_id in the PUT /api/ciphers/{id}/partial endpoint. While the standard retrieval API correctly enforces access controls, the partial update endpoint returns 200 OK and exposes sensitive cipherDetails including name, notes, data, and secureNote fields.
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< 1.35.4CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
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 checksWork through these to decide whether this CVE applies to you.
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Identify Vaultwarden versionCheck the version by querying the API endpoint /api/version or by inspecting the docker container image tag, or check the admin panel if enabled. Also check the running binary or container tag for the version number.Affected if The installed version is below 1.35.4 (e.g., 1.35.3, 1.35.0, older releases)
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Confirm user authentication is enabledVerify that the Vaultwarden instance has user registration or invitation enabled, allowing authenticated regular (non-admin) users to exist. Check the ADMIN_TOKEN and optionally SIGNUPS_ALLOWED configuration settings.Affected if The instance allows regular user accounts to be created or invited, and those users can authenticate to access the web vault or API
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Verify the partial cipher update endpoint existsCheck if the API endpoint PUT /api/ciphers/{id}/partial is accessible by attempting a request (with a valid auth token) to this endpoint or by reviewing Vaultwarden source code for the presence of this route handler.Affected if The endpoint responds to PUT requests with a valid auth token, indicating the vulnerable code path exists in this installation
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Review API access logs for unauthorized cipher access attemptsInspect Vaultwarden logs (stdout, stderr, or configured log files) for PUT requests to /api/ciphers/*/partial where the cipher_id does not belong to the authenticated user making the request. Look for 200 OK responses on cross-user cipher operations.Affected if Logs show PUT /api/ciphers/{id}/partial requests where the requesting user_id does not match the owner of the referenced cipher_id, indicating active exploitation attempts or successful IDOR exploitation
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Check for unexpected cipher data exposure in partial update responsesIf testing in a non-production environment, create two test users with separate ciphers. Authenticate as user A and send a PUT request to /api/ciphers/{cipher_id_of_user_b}/partial. Observe if the response returns 200 OK with user B's cipher details (name, notes, data, secureNote) instead of a 403 Forbidden.Affected if The partial update endpoint returns 200 OK and includes sensitive cipherDetails (name, notes, data, secureNote) from a cipher owned by a different user, confirming the IDOR vulnerability is present
A Vaultwarden instance is affected if it is running version 1.35.3 or earlier, has active user accounts, and the PUT /api/ciphers/{id}/partial endpoint allows authenticated users to access or partially update ciphers belonging to other users.
Generated from the published advisory. Verify against your own configuration.
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 · scoped1.35.4
Upgrade Vaultwarden to version 1.35.4 or later to apply the security patch that corrects the authorization bypass in the partial cipher update endpoint.
Vaultwarden 1.35.4 or later
- 1. Check the current running version of Vaultwarden (e.g., via docker ps or system service status)
- 2. Backup your Vaultwarden data directory and configuration files before upgrading
- 3. Upgrade Vaultwarden to version 1.35.4 or later (e.g., docker pull vaultwarden/server:1.35.4 or update your deployment method)
- 4. Restart the Vaultwarden service/container
- 5. Verify the upgrade was successful by checking the version endpoint or admin page
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-27898 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-27898 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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