UndiciApplication · Node.js
CVE-2026-9678
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedImpact: Undici's cache interceptor incorrectly classifies some responses as cacheable when the upstream Cache-Control header uses whitespace-padded qualified private or no-cache field names such as private=" authorization" or no-cache="\tauthorization". The parser preserves the surrounding whitespace, so later comparisons against the literal authorization field name fail and the response is stored. In shared-cache mode, this allows a response containing one user's authenticated data to be served from cache to a subsequent caller, including an unauthenticated caller, when both requests resolve to the same cache key. Affected applications are those that explicitly enable the cache interceptor (interceptors.cache()) in shared mode, forward Authorization headers upstream, and receive cacheable responses with non-canonical qualified private or no-cache directives. Patches: Upgrade to undici v7.28.0 or v8.5.0. Workarounds: If upgrade is not immediately possible, disable shared-cache mode for traffic that includes Authorization headers, avoid caching responses to authenticated requests, or add Vary: Authorization upstream.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceUndici's cache interceptor incorrectly treats responses as cacheable when upstream Cache-Control headers contain whitespace-padded qualified directives like `private=' authorization'` or `no-cache=' authorization'`. The parser preserves surrounding whitespace, causing string comparisons against the literal 'authorization' field name to fail, allowing the response to be stored in shared cache despite containing authenticated data.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
UndiciApplication
>= 7.0.0, < 7.28.0>= 8.0.0, < 8.5.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed undici versionRun `npm list undici` or `node -p "require('undici/package.json').version"` to get the installed versionAffected if The version falls within >= 7.0.0 and < 7.28.0, or >= 8.0.0 and < 8.5.0
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Verify cache interceptor is in useSearch your codebase for imports of 'undici/cache' or usage of `fetch` with cache options like `cache: 'shared'` or custom cache implementationsAffected if Your application uses undici's cache interceptor or shared cache mode to store HTTP responses
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Inspect upstream Cache-Control headersLog or examine the Cache-Control header values returned by your upstream servers for responses to authenticated requestsAffected if Any upstream response contains whitespace-padded directives such as `private=' authorization'`, `no-cache='\tauthorization'`, or similar patterns with spaces or tabs around 'authorization' within quoted values
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Audit stored cache entriesIf you have access to the cache storage (file system, Redis, etc.), inspect cached responses to see if any contain Authorization header values or authenticated content that should not have been cachedAffected if Cached responses exist that were returned with an Authorization header present in the original request, indicating unauthorized caching of private data
You are affected if undici version is in the affected range, the cache interceptor is enabled, and your upstream servers return Cache-Control headers with whitespace-padded private/no-cache directives that are being incorrectly cached.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped7.28.08.5.0
Upgrade to undici v7.28.0 or v8.5.0. If immediate upgrade is not feasible, disable shared-cache mode for requests with Authorization headers, avoid caching responses to authenticated requests, or add Vary: Authorization header upstream.
undici v7.28.0 or v8.5.0
- Check the current undici version in your project by examining package.json or running npm list undici
- If using undici v7.x (version >= 7.0.0), upgrade to v7.28.0 by running: npm install [email protected]
- If using undici v8.x (version >= 8.0.0), upgrade to v8.5.0 by running: npm install [email protected]
- After upgrading, run your test suite to verify the application functions correctly
- If you encounter issues, review the changelog for any breaking changes between your current version and the target version
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Undici
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-9678 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-9678 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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