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CVE-2026-6733 low CVSS 3.7

Vulnerability in undici (CVE-2026-6733)

Summary

Vulnerability in undici (CVE-2026-6733). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 8.5.0 or later.

Original description

The description as published by the source.

Impact

Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When the client dispatches the next request on that socket, it associates the injected response with the new request, causing responses to be delivered to the wrong requests.

This requires an attacker-controlled or compromised upstream HTTP/1.1 server and keep-alive connection reuse.

Patches

Upgrade to undici v6.27.0, v7.28.0 or v8.5.0.

Workarounds

Disable keep-alive connection reuse by setting keepAliveTimeout: 0 on the Client or Pool.

Source: NIST National Vulnerability Database NVD GitHub Advisory

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-2026-6733 has been found in undici.
Risk of unauthorized operations or information disclosure. CVSS score: 3.7/10.
What to do: upgrade undici to 8.5.0 or later.
If unsure, ask your IT team or search "undici CVE-2026-6733" on the vendor's site.

CVE-2026-6733 (undici) — CWE-367 / CVSS v3 3.7
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 8.5.0 — apply immediately
Workaround: Disable keep-alive connection reuse by setting keepAliveTimeout: 0 on the Client or Pool.
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-367) exists in undici.

📍 Affected scope

Check the vendor advisory for the affected versions of undici.

🔥 Severity

Severity: Low (CVSS 3.7/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 8.5.0.

🛡️ Workaround

Workaround: Disable keep-alive connection reuse by setting keepAliveTimeout: 0 on the Client or Pool.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'undici' . 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 'undici' . | 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 undici 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 
    Disable keep-alive connection reuse by setting `keepAliveTimeout: 0` on the Client or Pool.

    パッチが適用されるまでの応急処置として、Disable keep-alive connection reuse by setting keepAliveTimeout: 0 on the Client or Pool. 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 undici to 8.5.0

    ステージング環境で 8.5.0 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 undici
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.5.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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