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CVE-2021-43840

MEDIUM
Published 2021-12-17T18:15:11
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CVSS Score

V3.1
4.4
/10
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N
Base Score Metrics
Exploitability: N/A Impact: N/A

EPSS Score

v2025.03.14
0.002
probability
of exploitation in the wild

There is a 0.2% chance that this vulnerability will be exploited in the wild within the next 30 days.

Updated: 2025-06-25
Exploit Probability
Percentile: 0.459
Higher than 45.9% of all CVEs

Attack Vector Metrics

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED

Impact Metrics

Confidentiality
HIGH
Integrity
NONE
Availability
NONE

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.

Available Exploits

No exploits available for this CVE.

Related News

No news articles found for this CVE.

Affected Products

discourse

message_bus

Affected Versions:

< 3.3.7

GitHub Security Advisories

Community-driven vulnerability intelligence from GitHub

✓ GitHub Reviewed MODERATE

Path traversal when MessageBus::Diagnostics is enabled

GHSA-xmgj-5fh3-xjmm

Advisory Details

### Impact Users who deployed message bus with diagnostics features enabled (default off) were 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. ### Patches Patched in 3.3.7. ### Workarounds Disable MessageBus::Diagnostics in production like environments.

Affected Packages

RubyGems message_bus
ECOSYSTEM: ≥0 <3.3.7

CVSS Scoring

CVSS Score

5.0

CVSS Vector

CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:N/A:N

References

WEB https://github.com/discourse/message_bus/security/advisories/GHSA-xmgj-5fh3-xjmm
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2021-43840
WEB https://github.com/discourse/message_bus/commit/9b6deee01ed474c7e9b5ff65a06bb0447b4db2ba
PACKAGE https://github.com/discourse/message_bus
WEB https://github.com/rubysec/ruby-advisory-db/blob/master/gems/message_bus/CVE-2021-43840.yml

Advisory provided by GitHub Security Advisory Database. Published: December 17, 2021, Modified: December 17, 2021

References

https://github.com/discourse/message_bus/security/advisories/GHSA-xmgj-5fh3-xjmm
https://github.com/discourse/message_bus/commit/9b6deee01ed474c7e9b5ff65a06bb0447b4db2ba
Published: 2021-12-17T18:15:11
Last Modified: 2024-08-04T04:10:16.823Z
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