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CVE-2026-56385
medium
CVSS 4.3
Information Disclosure in craftcms/cms (CVE-2026-56385)
Summary
vulnerability in craftcms/cms (CVE-2026-56385). Risk of unauthorized operations or information disclosure. Exploitable via ``previewHtml``. Mitigation: upgrade to `4.17.8` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-56385** has been found in craftcms/cms.
Attackers can target a specific entry point like ``previewHtml`` over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 4.3/10.
What to do: upgrade craftcms/cms to **4.17.8** or later.
If unsure, ask your IT team or search "craftcms/cms CVE-2026-56385" on the vendor's site.
CVE-2026-56385 (craftcms/cms) — CWE-200 / CVSS v3 4.3
Attack vector: remote (network-reachable) / no user interaction
Attack surface: `previewHtml` / `assetId` / `canView` / `false`
Patched: `4.17.8` — 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
**information disclosure** (CWE-200) exists in craftcms/cms. Attackers reach the vulnerable code path via ``previewHtml`` without authentication.
📍 Affected scope
craftcms/cms — . Attack surface: `previewHtml` / `assetId` / `canView` / `false`.
🔥 Severity
Severity: Medium (CVSS 4.3/10). Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **4.17.8**.
🛡️ 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 'craftcms/cms' .` 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 'craftcms/cms' . | 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 `craftcms/cms` 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 craftcms/cms to 4.17.8ステージング環境で 4.17.8 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
craftcms/cms
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.17.8"}]}]
References
- web https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27
- web https://github.com/craftcms/cms/security/advisories/GHSA-44px-qjjc-xrhq
- web https://www.vulncheck.com/advisories/craft-cms-authorization-bypass-in-assets-preview-file-endpoint
- web https://nvd.nist.gov/vuln/detail/CVE-2026-56385
- web https://github.com/advisories/GHSA-f4h3-qhg5-j6mq
- web https://github.com/craftcms/cms/commit/b1cddf72c98a66801beb04ea4b07e72182b7b7db
- web https://github.com/advisories/GHSA-44px-qjjc-xrhq