CVE-2021-43840

Path traversal in message_bus

Description

message_bus is a messaging bus for Ruby processes and web clients. In versions prior to 3.3.7 users who deployed message bus with diagnostics features enabled (default off) are 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. This issue has been patched in version 3.3.7. Users unable to upgrade should ensure that MessageBus::Diagnostics is disabled.

Category

4.4
CVSS
Severity: Medium
CVSS 3.1 •
CVSS 2.0 •
EPSS 0.22%
Third-Party Advisory github.com Third-Party Advisory github.com
Affected: discourse message_bus
Published at:
Updated at:

References

Frequently Asked Questions

What is the severity of CVE-2021-43840?
CVE-2021-43840 has been scored as a medium severity vulnerability.
How to fix CVE-2021-43840?
To fix CVE-2021-43840, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2021-43840 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2021-43840 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-43840?
CVE-2021-43840 affects discourse message_bus.
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