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CVE-2025-21756
high
CVSS 7.8
Use-After-Free in c (CVE-2025-21756)
Summary
vulnerability in c (CVE-2025-21756). Successful exploitation can lead to full system takeover.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2025-21756** has been found in c.
Successful exploitation can lead to full system takeover. CVSS score: 7.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "c CVE-2025-21756" on the vendor's site.
CVE-2025-21756 (c) — CWE-416 / CVSS v3 7.8
Attack vector: local / no user interaction
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
**use-after-free** (CWE-416) exists in c.
📍 Affected scope
c — .
🔥 Severity
Severity: High (CVSS 7.8/10). Successful exploitation can lead to full system takeover
🔧 How to fix
Update to the patched release per vendor advisory.
🛡️ 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 'c' .` 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 'c' . | 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 `c` を grep し、稼働しているサービス・バージョンを把握する。
-
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。
References
- web https://git.kernel.org/stable/c/3f43540166128951cc1be7ab1ce6b7f05c670d8b
- web https://git.kernel.org/stable/c/42b33381e5e1f2b967dc4fb4221ddb9aaf10d197
- web https://git.kernel.org/stable/c/645ce25aa0e67895b11d89f27bb86c9d444c40f8
- web https://git.kernel.org/stable/c/b1afd40321f1c243cffbcf40ea7ca41aca87fa5e
- web https://git.kernel.org/stable/c/e48fcb403c2d0e574c19683f09399ab4cf67809c
- web https://git.kernel.org/stable/c/e7754d564579a5db9c5c9f74228df5d6dd6f1173
- web https://git.kernel.org/stable/c/fcdd2242c0231032fc84e1404315c245ae56322a
- web https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
- web https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html
- web https://cert-portal.siemens.com/productcert/html/ssa-082556.html
- web https://cert-portal.siemens.com/productcert/html/ssa-265688.html
- web https://nvd.nist.gov/vuln/detail/CVE-2025-21756
- web https://github.com/hoefler02/CVE-2025-21756/blob/main/x.c
- web https://github.com/advisories/GHSA-5828-2c94-235c