Vulnerability in puma (CVE-2026-47736)
Summary
Vulnerability in puma (CVE-2026-47736). Risk of unauthorized operations or information disclosure. Exploitable via set_remote_address. Mitigation: upgrade to 7.2.1 or later.
Original description
The description as published by the source.
Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, when PROXY protocol v1 support is enabled, Puma reads incoming bytes into an internal buffer while waiting for CRLF to determine whether a PROXY v1 line is present, allowing an attacker that continuously sends bytes without CRLF to cause unbounded in-process memory growth and additional CPU cost from repeatedly scanning the growing buffer. This issue is fixed in versions 7.2.1 and 8.0.2.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
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-2026-47736 has been found in puma.
Attackers can target a specific entry point like set_remote_address over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade puma to 7.2.1 or later.
If unsure, ask your IT team or search "puma CVE-2026-47736" on the vendor's site.
CVE-2026-47736 (puma) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: set_remote_address / PROXY_PROTOCOL_V1_REGEX
Patched: 7.2.1 — 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 set_remote_address without authentication.
Check the vendor advisory for the affected versions of puma. Attack surface: set_remote_address / PROXY_PROTOCOL_V1_REGEX.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 7.2.1.
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
-
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 7.2.1ステージング環境で 7.2.1 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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-47736 puma Fixed in: 5.6.5-3+deb12u2
- Ubuntu UBUNTU-CVE-2026-47736 puma
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- patch github.com
- web github.com
- web cve.org
- web github.com
- web github.com
- web github.com