High severity · published Sep 29, 2026
CVE-2026-101878
Bitwarden Server 2025.6.0 < 2025.6.0 Authentication Bypass via SSO Identifier Truncation
7.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 17% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
BS
bitwarden server · bitwarden
2025.6.0 before 2026.5.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-101878
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-101878
technical-description
https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncation
release-notes
https://github.com/bitwarden/server/releases/tag/v2026.5.0
issue-tracking
https://github.com/bitwarden/server/pull/7501
patch
https://github.com/bitwarden/server/commit/27ae3d5455f723975fac03819eaeba8710666bc4
third-party-advisory
https://www.vulncheck.com/advisories/bitwarden-server-authentication-bypass-via-sso-identifier-truncation