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TI-2021-19646 Aliases CVE-2021-43840GHSA-xmgj-5fh3-xjmm

Path traversal in message_bus

Priority LOW 33CWE-22Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Information disclosure
Confidentiality · integrity · availability
High · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-22 and the CVSS impact.

Summary

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.

Why it matters now

EPSS 0.01947 80th percentileScored 2026-11-07
Fix Fixed message_bus (discourse): 3.3.7message_bus (RubyGems): 3.3.7

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
discoursemessage_busbefore 3.3.73.3.7Patch availableCNA
—message_bus (RubyGems)before 3.3.73.3.7Patch availableGHSA-xmgj-5fh3-xjmm
  • message_bus Vendordiscourse Affected before 3.3.7 Fixed in 3.3.7 Patch available CNA
  • message_bus (RubyGems) Vendor— Affected before 3.3.7 Fixed in 3.3.7 Patch available GHSA-xmgj-5fh3-xjmm

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:discourse:message_bus:*:*:*:*:*:ruby:*:*before 3.3.7Vulnerablediscourse
  • cpe:2.3:a:discourse:message_bus:*:*:*:*:*:ruby:*:* Versions before 3.3.7 Vulnerable ·discourse

Remediation

  • Fix · CNA message_bus (discourse) Fixed in 3.3.7
  • Fix · GHSA-xmgj-5fh3-xjmm message_bus (RubyGems) Fixed in 3.3.7 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-43840
  2. 2026-10-03 Alias added: GHSA-xmgj-5fh3-xjmm

References

Patch 1

Advisory 2

Other 2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences