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

Status: published. Published: 2026-09-29. Updated: 2026-11-08.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/bitwarden/server/pull/7501
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/bitwarden/server/commit/27ae3d5455f723975fac03819eaeba8710666bc4

## Affected products and versions

- bitwarden / bitwarden server (bitwarden/server): ≥ 2025.6.0; < 2026.5.0 (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 7.7 (high); 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; source: CNA: VulnCheck

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: 0.26% as of 2026-11-08; percentile 17.61%

- SSVC: exploitation poc; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-303

## Exploit evidence

- exploit: https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncation (CNA: VulnCheck)

## References

- https://sanjokkarki.com.np/blog/bitwarden-sso-externalid-truncation (CNA: VulnCheck; technical-description, exploit)

- https://github.com/bitwarden/server/releases/tag/v2026.5.0 (CNA: VulnCheck; release-notes)

- https://github.com/bitwarden/server/pull/7501 (CNA: VulnCheck; issue-tracking, patch)

- https://github.com/bitwarden/server/commit/27ae3d5455f723975fac03819eaeba8710666bc4 (CNA: VulnCheck; patch)

- https://www.vulncheck.com/advisories/bitwarden-server-authentication-bypass-via-sso-identifier-truncation (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-101878; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-101878; retrieved 2026-11-08; source updated Not reported

Revision: 5b8b997bfe1e5361ff5a74781b3f284fda923c3d831a3688f0f93028d3fa96d1

Canonical: https://y2.dev/cve/CVE-2026-101878

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.