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CVE-2021-21322

Vulnerability in fastify-http-proxy (CVE-2021-21322)

Summary

Vulnerability in fastify-http-proxy (CVE-2021-21322). Confidential information can be exposed externally. Mitigation: upgrade to 4.3.1 or later.

Original description

The description as published by the source.

Impact

By crafting a specific URL, it is possible to escape the prefix of the proxied backend service.
If the base url of the proxied server is /pub/, a user expect that accessing /priv on the target service would not be possible. Unfortunately, it is.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Patches

All releases after v4.3.1 include the fix.

Workarounds

There are no workaround available.

For more information

If you have any questions or comments about this advisory:

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2021-21322 has been found in fastify-http-proxy.
Confidential information can be exposed externally.
What to do: upgrade fastify-http-proxy to 4.3.1 or later.
If unsure, ask your IT team or search "fastify-http-proxy CVE-2021-21322" on the vendor's site.

CVE-2021-21322 (fastify-http-proxy) — CWE-20
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 4.3.1 — apply immediately
Workaround: There are no workaround available.
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 fastify-http-proxy.

📍 Affected scope

Check the vendor advisory for the affected versions of fastify-http-proxy.

🔥 Severity

Severity: ?. Confidential information can be exposed externally.

🔧 How to fix

Update to 4.3.1.

🛡️ Workaround

Workaround: There are no workaround available.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'fastify-http-proxy' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'fastify-http-proxy' . | 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 fastify-http-proxy を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply temporary workaround mitigate 
    There are no workaround available.

    パッチが適用されるまでの応急処置として、There are no workaround available. を実施。回避策の副作用 (機能低下) を確認した上で。

  3. 3
    Apply patch patch 
    Upgrade fastify-http-proxy to 4.3.1

    ステージング環境で 4.3.1 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を含めること。

  4. 4
    Post-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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm fastify-http-proxy
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.3.1"}]}]

References

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