Bitwarden Server 2025.6.0 < 2025.6.0 Authentication Bypass via SSO Identifier Truncation (CVE-2026-101878) | HOL Guard CVE

High · CVSS 7.7CVE-2026-101878

Bitwarden Server 2025.6.0 < 2025.6.0 Authentication Bypass via SSO Identifier Truncation

Answer in brief

CVE-2026-101878 records a High severity (CVSS 7.7) vulnerability in Bitwarden Server 2025.6.0 < 2025.6.0 Authentication Bypass via SSO Identifier Truncation. The current sources do not mark it as known exploited. The current feed maps bitwarden/bitwarden server (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 29, 2026Updated Sep 29, 2026Source checked Sep 29, 2026First seen by HOL Sep 29, 2026Material review Sep 29, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps bitwarden/bitwarden server (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
bitwarden/bitwarden servergeneric	>=2025.6.0 <2026.5.0	2026.5.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for bitwarden/bitwarden server.
Review the reported fix. Update bitwarden/bitwarden server to 2026.5.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 29, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.