CVE-2026-101878 Bitwarden Server 2025.6.0 < 2025.6.0 Authentication Bypass via SSO Identifier Truncation
Attackers can bypass authentication and impersonate users by exploiting SSO identifier truncation in SQL Server deployments of Bitwarden Server.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-101878?
CVE-2026-101878 is a high-severity authentication bypass vulnerability in bitwarden server, published on 29 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-303
Which versions are affected by CVE-2026-101878?
How do I fix CVE-2026-101878?
No fix has been published for CVE-2026-101878 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-101878 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101878 exists.
Sources
Also known as GHSA-2fcc-4gv4-mvr7.