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CVE-2026-33555
medium
CVSS 4.0
Vulnerability in haproxy (CVE-2026-33555)
Summary
vulnerability in haproxy (CVE-2026-33555). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to `3.3.6` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-33555** has been found in haproxy.
Risk of unauthorized operations or information disclosure. CVSS score: 4.0/10.
What to do: upgrade haproxy to **3.3.6** or later.
If unsure, ask your IT team or search "haproxy CVE-2026-33555" on the vendor's site.
CVE-2026-33555 (haproxy) — CWE-130 / CVSS v3 4.0
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: `3.3.6` — 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-130) exists in haproxy.
📍 Affected scope
haproxy — .
🔥 Severity
Severity: Medium (CVSS 4.0/10). Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **3.3.6**.
🛡️ 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 'haproxy' .` 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 'haproxy' . | 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 `haproxy` 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 haproxy to 3.3.6ステージング環境で 3.3.6 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
Bitnami
haproxy
[{"type":"SEMVER","events":[{"introduced":"2.6.0"},{"fixed":"3.3.6"}]}]
References
- web https://github.com/haproxy/haproxy/commit/05a295441c621089ffa4318daf0dbca2dd756a84
- web https://r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.html
- web https://www.haproxy.com/documentation/haproxy-aloha/changelog/
- web https://www.haproxy.org
- web https://www.mail-archive.com/[email protected]/msg46752.html
- web https://nvd.nist.gov/vuln/detail/CVE-2026-33555