OpenBao has Reflected XSS in its OIDC authentication error message

MEDIUM 6.1CVE-2026-33758 · BIT-openbao-2026-33758 · GHSA-cpj3-3r2f-xj59 · Published 27/03/2026 · updated 15/07/2026

In short

CVE-2026-33758 is a MEDIUM (CVSS 6.1) vulnerability affecting github.com/openbao/openbao, openbao (openbao).
Chance of exploitation in the next 30 days (EPSS): 0.30%, higher than 22.5% of all vulnerabilities.
Fix: update to 0.0.0-20260325133417-6e2b2dd84f0e, 2.5.2 or later.

Package	Affected versions	Patched versions
github.com/openbao/openbao Go	`< 0.0.0-20260325133417-6e2b2dd84f0e`	`0.0.0-20260325133417-6e2b2dd84f0e`
openbao openbao	`< 2.5.2`	`2.5.2`

Description

Impact

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.

Patches

The error_description parameter has been replaced with a static error message in v2.5.2

Workarounds

The vulnerability can be mitigated by removing any roles with callback_mode set to direct.

NVD description

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`.