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CVE-2026-12151 high CVSS 7.5

Vulnerability in undici (CVE-2026-12151)

Summary

Vulnerability in undici (CVE-2026-12151). Risk of unauthorized operations or information disclosure. Exploitable via maxPayloadSize. Mitigation: upgrade to 8.5.0 or later.

Original description

The description as published by the source.

Impact

The undici WebSocket client enforces maxPayloadSize on the cumulative byte count of fragments in a message but does not enforce a limit on the number of fragments. A malicious WebSocket server can stream many small or empty continuation frames that each pass per-frame and cumulative-size validation, collectively causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service.

Affected applications are those using the undici WebSocket client (new WebSocket(...)) or the WebSocketStream API that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint.

All releases starting at undici 6.17.0 are affected.

Patches

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

Workarounds

No workaround is available. The fix must be applied through an upgrade.

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-2026-12151 has been found in undici.
Attackers can target a specific entry point like maxPayloadSize over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade undici to 8.5.0 or later.
If unsure, ask your IT team or search "undici CVE-2026-12151" on the vendor's site.

CVE-2026-12151 (undici) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: maxPayloadSize / WebSocketStream
Patched: 8.5.0 — apply immediately
Workaround: No workaround is 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-400) exists in undici. Attackers reach the vulnerable code path via maxPayloadSize without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of undici. Attack surface: maxPayloadSize / WebSocketStream.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 8.5.0.

🛡️ Workaround

Workaround: No workaround is available.

🔍 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 
    No workaround is available.

    パッチが適用されるまでの応急処置として、No workaround is 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 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":"SEMVER","events":[{"introduced":"8.0.0"},{"fixed":"8.5.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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