Path Traversal in message_bus (CVE-2021-43840)
Summary
Path traversal in message_bus (CVE-2021-43840). Confidential information can be exposed externally. Exploitable via merge_slashes. Mitigation: upgrade to 3.3.7 or later.
Original description
The description as published by the source.
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.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2021-43840 has been found in message_bus.
Attackers can target a specific entry point like merge_slashes over the network to misuse the product.
Confidential information can be exposed externally.
What to do: upgrade message_bus to 3.3.7 or later.
If unsure, ask your IT team or search "message_bus CVE-2021-43840" on the vendor's site.
CVE-2021-43840 (message_bus) — CWE-22
Attack vector: remote (network-reachable)
Attack surface: merge_slashes
Patched: 3.3.7 — apply immediately
Workaround: Disable MessageBus::Diagnostics in production like environments.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Path traversal (CWE-22) exists in message_bus. Attackers reach the vulnerable code path via merge_slashes.
Check the vendor advisory for the affected versions of message_bus. Attack surface: merge_slashes.
Severity: ?. Confidential information can be exposed externally.
Update to 3.3.7.
Workaround: Disable MessageBus::Diagnostics in production like environments.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'message_bus' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'message_bus' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
message_busを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Disable MessageBus::Diagnostics in production like environments.パッチが適用されるまでの応急処置として、Disable MessageBus::Diagnostics in production like environments. を実施。回避策の副作用 (機能低下) を確認した上で。
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3Apply patch patch
Upgrade message_bus to 3.3.7ステージング環境で 3.3.7 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com