CVE-2026-33758 CRITICAL

CVE-2026-33758: OpenBao has Reflected XSS in its OIDC authentication error message

Vendor Openbao
Product openbao
Weakness CWE-20 · Input validation
Published March 27, 2026
Last update June 30, 2026
View on NVD All CVEs

CVSS base score

9.4/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction —
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

What the vulnerability does

01Description

OpenBao is an open source identity-based secrets management system. Prior to version 2.5.2, OpenBao installations that have an OIDC/JWT authentication method enabled and a role with `callback_mode=direct` configured are vulnerable to XSS via the `error_description` parameter on the page for a failed authentication. This allows an attacker access to the token used in the Web UI by a victim. The `error_description` parameter has been replaced with a static error message in v2.5.2. The vulnerability can be mitigated by removing any roles with `callback_mode` set to `direct`.

Key dates

02Disclosure timeline

March 27, 2026 CVE published
June 30, 2026 Record updated