Path traversal when MessageBus::Diagnostics is enabled

中 6.5CVE-2021-43840 · GHSA-xmgj-5fh3-xjmm · 17/12/2021 公開 · 17/06/2026 更新

要点

CVE-2021-43840 は message_bus, message bus (discourse) に影響する深刻度「中」 (CVSS 6.5) の脆弱性です。
今後30日間に悪用される確率（EPSS）：1.9%（全脆弱性の 80.2% より高い）。
対処：3.3.7 以降に更新してください。

パッケージ	影響を受けるバージョン	修正済みバージョン
message_bus RubyGems	`< 3.3.7`	`3.3.7`
message bus discourse	`< 3.3.7`	`3.3.7`

概要

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.

NVD の説明

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.