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CVE-2020-5247

Vulnerability in puma (CVE-2020-5247)

Summary

Vulnerability in puma (CVE-2020-5247). Data can be tampered with by attackers. Mitigation: upgrade to 4.3.3 or later.

Original description

The description as published by the source.

In Puma (RubyGem) before 4.3.2 and before 3.12.3, if an application using Puma allows untrusted input in a response header, an attacker can use newline characters (i.e. CR, LF or/r, /n) to end the header and inject malicious content, such as additional headers or an entirely new response body. This vulnerability is known as HTTP Response Splitting. While not an attack in itself, response splitting is a vector for several other attacks, such as cross-site scripting (XSS). This is related to CVE-2019-16254, which fixed this vulnerability for the WEBrick Ruby web server. This has been fixed in versions 4.3.2 and 3.12.3 by checking all headers for line endings and rejecting headers with those characters.

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-2020-5247 has been found in puma.
Data can be tampered with by attackers.
What to do: upgrade puma to 4.3.3 or later.
If unsure, ask your IT team or search "puma CVE-2020-5247" on the vendor's site.

CVE-2020-5247 (puma) — CWE-113
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 4.3.3 — 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.

❓ What is the problem

A vulnerability (CWE-113) exists in puma.

📍 Affected scope

Check the vendor advisory for the affected versions of puma.

🔥 Severity

Severity: ?. Data can be tampered with by attackers.

🔧 How to fix

Update to 4.3.3.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Apply patch patch 
    Upgrade puma to 4.3.3

    ステージング環境で 4.3.3 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。

  3. 3
    Post-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

RubyGems puma
[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0"},{"fixed":"4.3.3"}]}]
Bitnami ruby-min
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.3.1"},{"introduced":"2.4.0"},{"fixed":"2.4.8"},{"introduced":"2.5.0"},{"fixed":"2.5.7"},{"introduced":"2.6.0"},{"fixed":"2.6.5"}]}]
Bitnami ruby
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.3.1"},{"introduced":"2.4.0"},{"fixed":"2.4.8"},{"introduced":"2.5.0"},{"fixed":"2.5.7"},{"introduced":"2.6.0"},{"fixed":"2.6.5"}]}]

References

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