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CVE-2026-6734 high CVSS 7.5

Vulnerability in undici (CVE-2026-6734)

Summary

Vulnerability in undici (CVE-2026-6734). Successful exploitation can lead to full system takeover. Exploitable via Socks5ProxyAgent. Mitigation: upgrade to 8.2.0 or later.

Original description

The description as published by the source.

Impact

When using Socks5ProxyAgent, undici reuses a single connection pool across different origins without verifying that the pool's origin matches the requested origin. All requests are dispatched through the pool connected to the first origin, regardless of the intended destination.

This causes cross-origin request routing: credentials and request data intended for origin B are sent to origin A, responses from the wrong origin are trusted, and HTTPS requests may be silently downgraded to HTTP.

Impacted users are applications that use Socks5ProxyAgent (directly or via setGlobalDispatcher) and make requests to more than one origin.

This was introduced in undici 7.23.0 via #4385 and affects all versions through 8.1.0.

Patches

Upgrade to undici v7.28.0 or v8.2.0

Workarounds

Use a separate Socks5ProxyAgent instance per origin, or avoid using Socks5ProxyAgent with multiple origins.

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-2026-6734 has been found in undici.
Attackers can target a specific entry point like Socks5ProxyAgent over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 7.5/10.
What to do: upgrade undici to 8.2.0 or later.
If unsure, ask your IT team or search "undici CVE-2026-6734" on the vendor's site.

CVE-2026-6734 (undici) — CWE-346 / CVSS v3 7.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: Socks5ProxyAgent / setGlobalDispatcher
Patched: 8.2.0 — apply immediately
Workaround: Use a separate Socks5ProxyAgent instance per origin, or avoid using Socks5ProxyAgent with multiple origins.
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-346) exists in undici. Attackers reach the vulnerable code path via Socks5ProxyAgent.

📍 Affected scope

Check the vendor advisory for the affected versions of undici. Attack surface: Socks5ProxyAgent / setGlobalDispatcher.

🔥 Severity

Severity: High (CVSS 7.5/10). Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 8.2.0.

🛡️ Workaround

Workaround: Use a separate Socks5ProxyAgent instance per origin, or avoid using Socks5ProxyAgent with multiple origins.

🔍 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 
    Use a separate `Socks5ProxyAgent` instance per origin, or avoid using `Socks5ProxyAgent` with multiple origins.

    パッチが適用されるまでの応急処置として、Use a separate Socks5ProxyAgent instance per origin, or avoid using Socks5ProxyAgent with multiple origins. 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 8.2.0

    ステージング環境で 8.2.0 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":"SEMVER","events":[{"introduced":"8.0.0"},{"fixed":"8.2.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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