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)
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.019 (78.7th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 79th percentile — 78.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.019 · newest: 0.019 · change: +0.000
Affected products
- Discourse Message Bus — versions < 3.3.7
Weakness classification (CWE)
References
- github.com/discourse/message_bus/security/advisories/GHSA-xmgj-5fh3-xjmm (Third Party Advisory)
- github.com/discourse/message_bus/commit/9b6deee01ed474c7e9b5ff65a06bb0447b4db2ba (Patch, Third Party Advisory)
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.