OpenBao up to 2.5.1 JWT/OIDC callback_mode session fixiation

Summaryinfo

A vulnerability was found in OpenBao up to 2.5.1. It has been rated as critical. This affects the function callback_mode of the component JWT/OIDC. The manipulation leads to session fixiation. This vulnerability is uniquely identified as CVE-2026-33757. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as critical, has been found in OpenBao up to 2.5.1. This issue affects the function callback_mode of the component JWT/OIDC. The manipulation with an unknown input leads to a session fixiation vulnerability. Using CWE to declare the problem leads to CWE-384. Authenticating a user, or otherwise establishing a new user session, without invalidating any existing session identifier gives an attacker the opportunity to steal authenticated sessions. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

OpenBao is an open source identity-based secrets management system. Prior to version 2.5.2, OpenBao does not prompt for user confirmation when logging in via JWT/OIDC and a role with `callback_mode` set to `direct`. This allows an attacker to start an authentication request and perform "remote phishing" by having the victim visit the URL and automatically log-in to the session of the attacker. Despite being based on the authorization code flow, the `direct` mode calls back directly to the API and allows an attacker to poll for an OpenBao token until it is issued. Version 2.5.2 includes an additional confirmation screen for `direct` type logins that requires manual user interaction in order to finish the authentication. This issue can be worked around either by removing any roles with `callback_mode=direct` or enforcing confirmation for every session on the token issuer side for the Client ID used by OpenBao.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-33757 since 03/23/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 304849 (Fedora 43 : openbao (2026-a9c2a486a6)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.5.2 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (304849). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Name

• OpenBao

Version

• 2.5.0
• 2.5.1

Website

• Product: https://github.com/openbao/openbao/

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Be aware that VulDB is the high quality source for vulnerability data.

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