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CVE-2026-33167
Cross-Site Scripting (XSS) in actionpack (CVE-2026-33167)
Summary
cross-site scripting in actionpack (CVE-2026-33167). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to `8.1.2.1` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-33167** has been found in actionpack.
Risk of unauthorized operations or information disclosure. CVSS score: ?/10.
What to do: upgrade actionpack to **8.1.2.1** or later.
If unsure, ask your IT team or search "actionpack CVE-2026-33167" on the vendor's site.
CVE-2026-33167 (actionpack) — CWE-79 /
Patched: `8.1.2.1` — 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.
❓ What is the problem
**Cross-site scripting (XSS)** (CWE-79) exists in actionpack.
📍 Affected scope
actionpack — .
🔥 Severity
Severity: ?. Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **8.1.2.1**.
🛡️ 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 'actionpack' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response Actions (7 steps)
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'actionpack' . | 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 `actionpack` を grep し、稼働しているサービス・バージョンを把握する。
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6Apply patch patch
Upgrade actionpack to 8.1.2.1ステージング環境で 8.1.2.1 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と、Step 3 で見つけた異常検知の続報チェックを含めること。
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7Post-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 Step 3 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
rubygems
actionpack
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.1.2.1"}]}]
References
- web https://github.com/rails/rails/security/advisories/GHSA-pgm4-439c-5jp6
- web https://github.com/rails/rails/commit/6752711c8c31d79ba50d13af6a6698a3b85415e0
- web https://github.com/rails/rails/releases/tag/v8.1.2.1
- web https://nvd.nist.gov/vuln/detail/CVE-2026-33167
- web https://github.com/rubysec/ruby-advisory-db/blob/master/gems/actionpack/CVE-2026-33167.yml
- web https://github.com/advisories/GHSA-pgm4-439c-5jp6