Path Traversal in Discourse Message Bus
CVE-2021-43840
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.
Vulnerability class: Path Traversal (Directory Traversal)
EPSS: 0.019 (77.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Discourse Message_bus — versions < 3.3.7
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Third Party Advisory)
- security-advisories@github.com (Patch, Third Party Advisory, x_refsource_MISC)
Frequently asked questions
- What is CVE-2021-43840?
- CVE-2021-43840 is a medium-severity vulnerability in Discourse Message Bus, classified under Path Traversal. CVSS score: 4.4/10. Published 2021-12-17.
- How severe is CVE-2021-43840?
- Medium severity. CVSS v3 base score is 4.4 out of 10.