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 members full 50-character identifier to authenticate as that member and obtain a victim-scoped access token.
Weakness
The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.
Related Attack Patterns
References
- https://github.com/bitwarden/server/commit/27ae3d5455f723975fac03819eaeba8710666bc4
- https://github.com/bitwarden/server/pull/7501
- https://github.com/bitwarden/server/releases/tag/v2026.5.0
- https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncation
- https://www.vulncheck.com/advisories/bitwarden-server-authentication-bypass-via-sso-identifier-truncation