CVE-2026-27898 | Vaultwarden: Unauthorized Access via Partial Update API on Another User’s Cipher

Vaultwarden 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.

Published: 2026-03-04 Last update: 2026-03-06 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-27898 is rated Low Risk (23.9/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.17%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-27898

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.03% 0.17% +0.14%
2 2026-03-05 — 0.03% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-27898

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.5 [email protected]

Weakness enumeration for CVE-2026-27898

GitHub Security Advisory for CVE-2026-27898

GHSA-w9f8-m526-h7fh · Severity: medium · Ecosystem: rust — Vaultwarden has Unauthorized Access via Partial Update API on Another User’s Cipher

OS Trackers for CVE-2026-27898

vendor priority summary link
alpine — CVE-2026-27898: 1 source package rows (vaultwarden); 18 state rows across 2 repos (3.23-community, edge-community); fixed 0, open 18. https://security.alpinelinux.org/vuln/CVE-2026-27898
redhat medium — https://access.redhat.com/security/cve/CVE-2026-27898

Affected software / configurations for CVE-2026-27898

Vendor Product Version Raw CPE
dani-garcia vaultwarden < 1.35.4 cpe:2.3:a:dani-garcia:vaultwarden:*:*:*:*:*:*:*:*

References for CVE-2026-27898

cvelogic Threat Intelligence