CVE-2026-101878
Bitwarden Server 2025.6.0 < 2025.6.0 Authentication Bypass via SSO Identifier Truncation
Bitwarden Server 2025.6.0 before 2026.5.0 declares the @ExternalId parameter of the User_ReadBySsoUserOrganizationIdExternalId stored procedure as NVARCHAR(50) while the column it queries stores NVARCHAR(300), silently truncating the SSO login identifier on SQL Server deployments and allowing a user whose identity-provider identifier begins with another organization member's full 50-character identifier to authenticate as that member and obtain a victim-scoped access token.
Fixes and workarounds
Fix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: VulnCheckFix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: VulnCheckAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| bitwarden server bitwarden bitwarden/server
github |
≥ 2025.6.0; < 2026.5.0 (affected, custom)
Other versions: unaffected |
CNA: VulnCheck |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 7.7 high |
CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N | CNA: VulnCheck |
| 3.1 / 7.5 high |
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H | CNA: VulnCheck |
Exploit evidence
- https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncation
exploit · CNA: VulnCheck
References
- https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncationCNA: VulnCheck · technical-description, exploit
- https://github.com/bitwarden/server/releases/tag/v2026.5.0CNA: VulnCheck · release-notes
- https://github.com/bitwarden/server/pull/7501CNA: VulnCheck · issue-tracking, patch
- https://github.com/bitwarden/server/commit/27ae3d5455f723975fac03819eaeba8710666bc4CNA: VulnCheck · patch
- https://www.vulncheck.com/advisories/bitwarden-server-authentication-bypass-via-sso-identifier-truncationCNA: VulnCheck · third-party-advisory
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