CVE-2026-101878: Incorrect Implementation of Authentication Algorithm in bitwarden bitwarden server
CVE-2026-101878 is a vulnerability in Bitwarden Server versions 2025.6.0 up to but not including 2026.5.0. It involves an incorrect implementation of an authentication algorithm where a stored procedure parameter truncates the SSO login identifier, allowing certain users to impersonate others within the same organization and obtain access tokens scoped to the victim.
AI Analysis
Technical Summary
Bitwarden Server versions from 2025.6.0 before 2026.5.0 contain a flaw in the User_ReadBySsoUserOrganizationIdExternalId stored procedure. The parameter @ExternalId is declared as NVARCHAR(50), but the corresponding database column stores NVARCHAR(300). This mismatch causes silent truncation of the SSO login identifier on SQL Server deployments. Consequently, a user whose identity-provider identifier starts with another organization member's full 50-character identifier can authenticate as that member and receive a victim-scoped access token.
Potential Impact
An attacker with a specially crafted SSO login identifier can impersonate another organization member by exploiting the truncation issue, potentially gaining unauthorized access to that member's resources within Bitwarden Server. This impacts confidentiality and integrity of user sessions and data.
Mitigation Recommendations
A fix is available in Bitwarden Server version 2026.5.0 and later. Users should upgrade to version 2026.5.0 or newer to resolve this vulnerability.
CVE-2026-101878: Incorrect Implementation of Authentication Algorithm in bitwarden bitwarden server
Description
CVE-2026-101878 is a vulnerability in Bitwarden Server versions 2025.6.0 up to but not including 2026.5.0. It involves an incorrect implementation of an authentication algorithm where a stored procedure parameter truncates the SSO login identifier, allowing certain users to impersonate others within the same organization and obtain access tokens scoped to the victim.
CVSS v4.0
Score 7.7high
Affected software
bitwarden
bitwarden server
pkg:github/bitwarden serverRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Bitwarden Server versions from 2025.6.0 before 2026.5.0 contain a flaw in the User_ReadBySsoUserOrganizationIdExternalId stored procedure. The parameter @ExternalId is declared as NVARCHAR(50), but the corresponding database column stores NVARCHAR(300). This mismatch causes silent truncation of the SSO login identifier on SQL Server deployments. Consequently, a user whose identity-provider identifier starts with another organization member's full 50-character identifier can authenticate as that member and receive a victim-scoped access token.
Potential Impact
An attacker with a specially crafted SSO login identifier can impersonate another organization member by exploiting the truncation issue, potentially gaining unauthorized access to that member's resources within Bitwarden Server. This impacts confidentiality and integrity of user sessions and data.
Mitigation Recommendations
A fix is available in Bitwarden Server version 2026.5.0 and later. Users should upgrade to version 2026.5.0 or newer to resolve this vulnerability.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-09-28T15:44:45.389Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6abb1feff7a7c54106a524ae
Added to database: 09/29/2026, 02:18:23 UTC
Last enriched: 09/29/2026, 02:32:45 UTC
Last updated: 09/29/2026, 02:32:45 UTC
Views: 5
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.