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CVE-2026-40176
high
CVSS 7.8
Vulnerability in composer/composer (CVE-2026-40176)
Summary
vulnerability in composer/composer (CVE-2026-40176). Successful exploitation can lead to full system takeover. Mitigation: upgrade to `2.2.27` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-40176** has been found in composer/composer.
Successful exploitation can lead to full system takeover. CVSS score: 7.8/10.
What to do: upgrade composer/composer to **2.2.27** or later.
If unsure, ask your IT team or search "composer/composer CVE-2026-40176" on the vendor's site.
CVE-2026-40176 (composer/composer) — CWE-20 / CVSS v3 7.8
Attack vector: local / unauthenticated
Patched: `2.2.27` — 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-20) exists in composer/composer.
📍 Affected scope
composer/composer — .
🔥 Severity
Severity: High (CVSS 7.8/10). Successful exploitation can lead to full system takeover
🔧 How to fix
Update to **2.2.27**.
🛡️ 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 'composer/composer' .` 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
-
1Identify exposure identify
grep -r 'composer/composer' . | 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 `composer/composer` を grep し、稼働しているサービス・バージョンを把握する。
-
6Apply patch patch
Upgrade composer/composer to 2.2.27ステージング環境で 2.2.27 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。
-
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
composer
composer/composer
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.2.27"}]}]
Bitnami
composer
[{"type":"SEMVER","events":[{"introduced":"1.0.0"},{"fixed":"2.2.27"},{"introduced":"2.3.0"},{"fixed":"2.9.6"}]}]
References
- web https://github.com/composer/composer/releases/tag/2.9.6
- web https://github.com/composer/composer/security/advisories/GHSA-wg36-wvj6-r67p
- web https://access.redhat.com/errata/RHSA-2026:8165
- web https://access.redhat.com/security/cve/CVE-2026-40176
- web https://bugzilla.redhat.com/show_bug.cgi?id=2458828
- web https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40176.json
- web https://github.com/FriendsOfPHP/security-advisories/blob/master/composer/composer/CVE-2026-40176.yaml
- web https://nvd.nist.gov/vuln/detail/CVE-2026-40176
- web https://github.com/advisories/GHSA-wg36-wvj6-r67p