CVE-2021-43840: Path traversal in message_bus

First published: Fri Dec 17 2021(Updated: )

### Impact Users who deployed message bus with diagnostics features enabled (default off) were vulnerable to a path traversal bug, which could lead to disclosure of secret information on a machine if an unintended user were to gain access to the diagnostic route. The impact is also greater if there is no proxy for your web application as the number of steps up the directories is not bounded. For deployments which uses a proxy, the impact varies. For example, If a request goes through a proxy like Nginx with `merge_slashes` enabled, the number of steps up the directories that can be read is limited to 3 levels. ### Patches Patched in 3.3.7. ### Workarounds Disable MessageBus::Diagnostics in production like environments.

Credit: security-advisories@github.com security-advisories@github.com security-advisories@github.com

Affected Software	Affected Version	How to fix
rubygems/message_bus	<3.3.7	3.3.7
Discourse Message Bus	<3.3.7
	<3.3.7

Remedy

https://github.com/discourse/message_bus/commit/9b6deee01ed474c7e9b5ff65a06bb0447b4db2ba

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