CVE-2021-43840
Published: 17 December 2021
Summary
CVE-2021-43840 is a medium-severity Path Traversal (CWE-22) vulnerability in Discourse Message Bus. Its CVSS base score is 4.4 (Medium).
Operationally, ranked at the 46.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-2612
Vulnerability details
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…
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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.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Validates pathnames and filenames to prevent traversal outside intended directories.