CVE-2026-101878
CVE-2026-101878 is a high-severity vulnerability with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-303.
Key facts
- Severity: High (CVSS 3.x base score 7.5)
- CVSS v4: 7.7
- EPSS exploit prediction: 0% (16th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-303
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2026-101878?
- 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.
- How severe is CVE-2026-101878?
- CVE-2026-101878 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2026-101878 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-101878?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- When was CVE-2026-101878 published?
- CVE-2026-101878 was published on 2026-09-29 and last updated on 2026-09-30.
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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