CVE-2026-101878highCWE-303

CVE-2026-101878: high-severity vulnerability in bitwarden server

Bitwarden Server 2025.6.0 < 2025.6.0 Authentication Bypass via SSO Identifier Truncation

Published · Updated

41Vexday Risk Score

No sign of exploitation. It has a public proof of concept.

ssvc Attendcvss 7.7epss 0.3%
exploitation probability
0.3%top 84% of all CVEs
observed exploitation
nono source reports it
1 public exploit(s)
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.
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
Affected products
bitwarden · bitwarden server
public PoCs found — 1
cve_referencesanjokkarki.com.np/blog/bitwarden-sso-externalid-truncationunverified
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
References
https://github.com/bitwarden/server/commit/27ae3d5455f723975fac03819eaeba8710666bc4https://github.com/bitwarden/server/pull/7501https://github.com/bitwarden/server/releases/tag/v2026.5.0https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncationhttps://www.vulncheck.com/advisories/bitwarden-server-authentication-bypass-via-sso-identifier-truncation