Vulnerability in puma (CVE-2021-29509)
Summary
Vulnerability in puma (CVE-2021-29509). Risk of unauthorized operations or information disclosure. Exploitable via puma. Mitigation: upgrade to 5.3.1 or later.
Original description
The description as published by the source.
Puma is a concurrent HTTP 1.1 server for Ruby/Rack applications. The fix for CVE-2019-16770 was incomplete. The original fix only protected existing connections that had already been accepted from having their requests starved by greedy persistent-connections saturating all threads in the same process. However, new connections may still be starved by greedy persistent-connections saturating all threads in all processes in the cluster. A puma server which received more concurrent keep-alive connections than the server had threads in its threadpool would service only a subset of connections, denying service to the unserved connections. This problem has been fixed in puma 4.3.8 and 5.3.1. Setting queue_requests false also fixes the issue. This is not advised when using puma without a reverse proxy, such as nginx or apache, because you will open yourself to slow client attacks (e.g. slowloris). The fix is very small and a git patch is available for those using unsupported versions of Puma.
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-2021-29509 has been found in puma.
Attackers can target a specific entry point like puma over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade puma to 5.3.1 or later.
If unsure, ask your IT team or search "puma CVE-2021-29509" on the vendor's site.
CVE-2021-29509 (puma) — CWE-400
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: puma / nginx / apache
Patched: 5.3.1 — apply immediately
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.
A vulnerability (CWE-400) exists in puma. Attackers reach the vulnerable code path via puma without authentication.
Check the vendor advisory for the affected versions of puma. Attack surface: puma / nginx / apache.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 5.3.1.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'puma' . 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 'puma' . | 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
pumaを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade puma to 5.3.1ステージング環境で 5.3.1 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。
-
3Post-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
- advisory github.com
- advisory lists.debian.org
- advisory rubygems.org
- advisory security.gentoo.org
- package github.com
- patch github.com
- patch gist.github.com
- web github.com