Reference page — cumulative record through Saturday, October 3, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-101878

CVE-2026-101878HIGH

Bitwarden Server 2025.6.0 < 2025.6.0 Authentication Bypass via SSO Identifier Truncation

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   H   N   L   N   H   H   H    7.7   .0026   15.9     —

AFFECTED
  Product           Versions    Fixed
  bitwarden server  2025.6.0 –  —

TIMELINE
  Sep 28  Reserved by VulnCheck
  Sep 29  Published (CNA: VulnCheck)
  Oct 1   EXPLOIT PUBLISHED — CVE-2026-101878 (bitwarden server). Public exploit reference added.

CWE-303 · CNA: VulnCheck · CVSS v4.0 · 5 references · NVD status: Awaiting Analysis

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
September 28, 2026	Reserved	Reserved by VulnCheck
September 29, 2026	Published	Published (CNA: VulnCheck)
October 1, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-101878 (bitwarden server). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
bitwarden	bitwarden server	—	2025.6.0	—

Weaknesses

CWE-303

References (5)

https://github.com/bitwarden/server/commit/27ae3d5455f723975fac03819eaeba8710666bc4 [patch]
https://github.com/bitwarden/server/pull/7501 [issue-tracking]
https://github.com/bitwarden/server/releases/tag/v2026.5.0 [release-notes]
https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncation [technical-description, exploit]
https://www.vulncheck.com/advisories/bitwarden-server-authentication-bypass-via-sso-identifier-truncation [third-party-advisory]

Authoritative record: CVE-2026-101878 at cve.org

Vendors: bitwarden

Weaknesses: CWE-303

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-101878 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Saturday, October 3, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.