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CVE-2021-33503
Vulnerability in urllib3 (CVE-2021-33503)
Summary
vulnerability in urllib3 (CVE-2021-33503). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to `1.26.5` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2021-33503** has been found in urllib3.
Risk of unauthorized operations or information disclosure. CVSS score: ?/10.
What to do: upgrade urllib3 to **1.26.5** or later.
If unsure, ask your IT team or search "urllib3 CVE-2021-33503" on the vendor's site.
CVE-2021-33503 (urllib3) — CWE-400 /
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: `1.26.5` — 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-400) exists in urllib3.
📍 Affected scope
urllib3 — .
🔥 Severity
Severity: ?. Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **1.26.5**.
🛡️ 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 'urllib3' .` 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
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1Identify exposure identify
grep -r 'urllib3' . | 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 `urllib3` 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 urllib3 to 1.26.5ステージング環境で 1.26.5 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
PyPI
urllib3
[{"type":"ECOSYSTEM","events":[{"introduced":"1.25.4"},{"fixed":"1.26.5"}]}]
pip
urllib3
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.26.5"}]}]
References
- advisory https://github.com/advisories/GHSA-q2q7-5pp4-w6pg
- advisory https://nvd.nist.gov/vuln/detail/CVE-2021-33503
- package https://github.com/urllib3/urllib3
- web https://github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec
- web https://github.com/urllib3/urllib3/security/advisories/GHSA-q2q7-5pp4-w6pg
- web https://security.gentoo.org/glsa/202107-36
- web https://www.oracle.com/security-alerts/cpuoct2021.html
- web https://github.com/urllib3/urllib3/commit/5b047b645f5f93900d5e2fc31230848c25eb1f5f#diff-52026d639119bf1e0364836b4e8a18bd9ed3c95c6ba39b26534a5057a65e35bbR65
- web https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2021-108.yaml
- web https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/6SCV7ZNAHS3E6PBFLJGENCDRDRWRZZ6W
- web https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/FMUGWEAUYGGHTPPXT6YBD53WYXQGVV73