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CVE-2026-43966
medium
CVSS 5.3
Vulnerability in cowlib (CVE-2026-43966)
Summary
vulnerability in cowlib (CVE-2026-43966). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to `2.16.0` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-43966** has been found in cowlib.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade cowlib to **2.16.0** or later.
If unsure, ask your IT team or search "cowlib CVE-2026-43966" on the vendor's site.
CVE-2026-43966 (cowlib) — CWE-113 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: `2.16.0` — 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-113) exists in cowlib.
📍 Affected scope
cowlib — .
🔥 Severity
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **2.16.0**.
🛡️ 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 'cowlib' .` 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 'cowlib' . | 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 `cowlib` 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 cowlib to 2.16.0ステージング環境で 2.16.0 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
Hex
cowlib
[{"type":"SEMVER","events":[{"introduced":"2.9.0"}]}]
erlang
cowboy
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.16.0"}]}]
erlang
gun
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.16.0"}]}]
References
- advisory 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
- advisory 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
- package https://hex.pm/packages/cowlib
- patch 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
- patch 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
- web https://nvd.nist.gov/vuln/detail/CVE-2026-43966
- web https://github.com/advisories/GHSA-w4f7-4cxr-rv3c
- web https://github.com/ninenines/cowlib/pull/163#issuecomment-4952645232
- web https://github.com/ninenines/cowlib/pull/166#issuecomment-5067554701