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CVE-2026-13697 high CVSS 7.4

Information Disclosure in undici (CVE-2026-13697)

Summary

Vulnerability in undici (CVE-2026-13697). Confidential information can be exposed externally. Exploitable via private. Mitigation: upgrade to 8.9.0 or later.

Original description

The description as published by the source.

Summary

Two issues in undici's cache interceptor, both fixed by the same patch on lib/util/cache.js:

  1. Shared-cache disclosure: Responses with malformed qualified Cache-Control: private directives such as private="" or private="," can be incorrectly stored in the default shared cache, then served to a later caller with the same cache key.
  2. Parse-time crash: Mixed unqualified-and-qualified private directives in the same header (such as public, max-age=60, private, private="hdr") cause an uncaught TypeError in the cache-control parser, terminating the request.

Impact

Shared-cache disclosure

Applications using interceptors.cache() in shared mode may cache a user-specific response and serve it to a later caller with the same cache key. This can disclose private response bodies and headers, including Set-Cookie.

Required conditions:

  • the cache interceptor is enabled in shared mode, including the default configuration;
  • an upstream returns a malformed directive such as Cache-Control: public, max-age=300, private="";
  • another request later matches the same cache key, without a separating Vary header.

Parse-time crash

Applications using interceptors.cache() against an upstream that returns a Cache-Control header combining unqualified private with qualified private="..." see an uncaught TypeError: output.private.concat is not a function during response handling. The request rejects; depending on the consumer's er…

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-2026-13697 has been found in undici.
Attackers can target a specific entry point like private over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.4/10.
What to do: upgrade undici to 8.9.0 or later.
If unsure, ask your IT team or search "undici CVE-2026-13697" on the vendor's site.

CVE-2026-13697 (undici) — CWE-200 / CVSS v3 7.4
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: private / TypeError / Vary / concat
Patched: 8.9.0 — apply immediately
Workaround: Until patched, avoid shared interceptors.cache() for user-specific responses, use type: 'private', or disable caching for affected 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

Information disclosure (CWE-200) exists in undici. Attackers reach the vulnerable code path via private without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of undici. Attack surface: private / TypeError / Vary / concat.

🔥 Severity

Severity: High (CVSS 7.4/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 8.9.0.

🛡️ Workaround

Workaround: Until patched, avoid shared interceptors.cache() for user-specific responses, use type: 'private', or disable caching for affected 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 
    Until patched, avoid shared `interceptors.cache()` for user-specific responses, use `type: 'private'`, or disable caching for affected origins.

    パッチが適用されるまでの応急処置として、Until patched, avoid shared interceptors.cache() for user-specific responses, use type: 'private', or disable caching for affected 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 8.9.0

    ステージング環境で 8.9.0 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":"8.9.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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