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CVE-2026-39850
high
CVSS 7.4
Vulnerability in yiisoft/yii2 (CVE-2026-39850)
Summary
vulnerability in yiisoft/yii2 (CVE-2026-39850). Confidential information can be exposed externally. Exploitable via ``require``. Mitigation: upgrade to `2.0.55` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-39850** has been found in yiisoft/yii2.
Attackers can target a specific entry point like ``require`` over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.4/10.
What to do: upgrade yiisoft/yii2 to **2.0.55** or later.
If unsure, ask your IT team or search "yiisoft/yii2 CVE-2026-39850" on the vendor's site.
CVE-2026-39850 (yiisoft/yii2) — CWE-20 / CVSS v3 7.4
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: `require` / `_file_`
Patched: `2.0.55` — 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 yiisoft/yii2. Attackers reach the vulnerable code path via ``require`` without authentication.
📍 Affected scope
yiisoft/yii2 — . Attack surface: `require` / `_file_`.
🔥 Severity
Severity: High (CVSS 7.4/10). Confidential information can be exposed externally
🔧 How to fix
Update to **2.0.55**.
🛡️ 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 'yiisoft/yii2' .` 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 'yiisoft/yii2' . | 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 `yiisoft/yii2` 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 yiisoft/yii2 to 2.0.55ステージング環境で 2.0.55 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
composer
yiisoft/yii2
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.55"}]}]
Packagist
yiisoft/yii2
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.55"}]}]
References
- advisory https://nvd.nist.gov/vuln/detail/CVE-2026-39850
- package https://github.com/yiisoft/yii2
- web https://github.com/yiisoft/yii2/security/advisories/GHSA-5vpg-rj7q-qpw2
- web https://github.com/yiisoft/yii2/commit/109878b491dbffa541032bc99fb5e26d12cd0375
- web https://github.com/yiisoft/yii2/releases/tag/2.0.55
- web https://github.com/advisories/GHSA-5vpg-rj7q-qpw2