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Path traversal when MessageBus::Diagnostics is enabled

Moderate severity GitHub Reviewed Published Dec 17, 2021 in discourse/message_bus • Updated May 4, 2023

Package

bundler message_bus (RubyGems)

Affected versions

< 3.3.7

Patched versions

3.3.7

Description

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.

References

@SamSaffron SamSaffron published to discourse/message_bus Dec 17, 2021
Published by the National Vulnerability Database Dec 17, 2021
Reviewed Dec 17, 2021
Published to the GitHub Advisory Database Dec 17, 2021
Last updated May 4, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
High
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:N/A:N

EPSS score

0.071%
(33rd percentile)

Weaknesses

CVE ID

CVE-2021-43840

GHSA ID

GHSA-xmgj-5fh3-xjmm

Source code

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