Bokeh up to 3.8.1 Websocket Connection missing origin validation in websockets

Summaryinfo

A vulnerability was found in Bokeh up to 3.8.1 and classified as critical. The affected element is an unknown function of the component Websocket Connection Handler. Executing a manipulation can lead to missing origin validation in websockets. The identification of this vulnerability is CVE-2026-21883. The attack may be launched remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Bokeh up to 3.8.1. This vulnerability affects an unknown code of the component Websocket Connection Handler. The manipulation with an unknown input leads to a missing origin validation in websockets vulnerability. The CWE definition for the vulnerability is CWE-1385. The product uses a WebSocket, but it does not properly verify that the source of data or communication is valid. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Bokeh is an interactive visualization library written in Python. In versions 3.8.1 and below, if a server is configured with an allowlist (e.g., dashboard.corp), an attacker can register a domain like dashboard.corp.attacker.com (or use a subdomain if applicable) and lure a victim to visit it. The malicious site can then initiate a WebSocket connection to the vulnerable Bokeh server. Since the Origin header (e.g., http://dashboard.corp.attacker.com/) matches the allowlist according to the flawed logic, the connection is accepted. Once connected, the attacker can interact with the Bokeh server on behalf of the victim, potentially accessing sensitive data, or modifying visualizations. This issue is fixed in version 3.8.2.

The advisory is available at github.com. This vulnerability was named CVE-2026-21883 since 01/05/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available.

Upgrading to version 3.8.2 eliminates this vulnerability. Applying the patch cedd113b0e271b439dce768671685cf5f861812e is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

• Bokeh

Version

• 3.8.0
• 3.8.1

License

• open-source

Website

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

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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