What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-29 · updated 2026-09-30
• Weakness: CWE-303

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.

Affected products

• bitwarden server: from 2025.6.0 before 2026.5.0 — fixed in 2026.5.0

How to fix

Upgrade to a fixed version: bitwarden server 2026.5.0. Check the vendor advisory for mitigations.

References

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

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