UndiciApplication · Node.js
CVE-2026-2581
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 · uneditedThis is an uncontrolled resource consumption vulnerability (CWE-400) that can lead to Denial of Service (DoS). In vulnerable Undici versions, when interceptors.deduplicate() is enabled, response data for deduplicated requests could be accumulated in memory for downstream handlers. An attacker-controlled or untrusted upstream endpoint can exploit this with large/chunked responses and concurrent identical requests, causing high memory usage and potential OOM process termination. Impacted users are applications that use Undici’s deduplication interceptor against endpoints that may produce large or long-lived response bodies. PatchesThe issue has been patched by changing deduplication behavior to stream response chunks to downstream handlers as they arrive (instead of full-body accumulation), and by preventing late deduplication when body streaming has already started. Users should upgrade to the first official Undici (and Node.js, where applicable) releases that include this patch.
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 confidenceThis is an uncontrolled resource consumption vulnerability (CWE-400) in Undici's HTTP client library. When the deduplication interceptor is enabled, response data for deduplicated requests accumulates in memory rather than streaming to downstream handlers, allowing attackers to cause memory exhaustion through large or chunked responses combined with concurrent identical requests, potentially leading to OOM process termination.
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
>= 7.17.0, < 7.24.0CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
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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Identify Undici version in your projectRun 'npm list undici' in your project directory, or check package.json dependencies, or require('undici/package.json').version in Node.jsAffected if The installed version is >= 7.17.0 and < 7.24.0
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Verify deduplication interceptor is in useSearch your codebase for 'undici' import statements and check if 'MockInterceptor' with 'reply' or 'delay' is used, or if you explicitly create interceptors with duplicate handling enabled. Check for patterns like new Dispatcher() with deduplication options or mock setup code.Affected if Your application explicitly uses Undici's mocking/deduplication interceptor for HTTP requests
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Identify endpoints receiving large or chunked responsesAudit your Undici request destinations. Look for API calls that return streaming data, large payloads, or chunked transfer encoding. Review request handlers that process variable-sized response bodies.Affected if Your Undici client makes requests to endpoints returning large, streaming, or chunked response bodies
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Check for concurrent identical request patternsReview application logic for scenarios where multiple simultaneous requests may be made to the same URL. Look for async operations, loops, or event-driven code that triggers duplicate HTTP calls within short time windows (milliseconds to seconds apart).Affected if Your application can trigger multiple concurrent requests to identical URLs within a deduplication window
You are affected if your Undici version is >= 7.17.0 and < 7.24.0 AND you use the deduplication interceptor with endpoints returning large/streaming responses AND your app can fire concurrent identical requests.
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 · scoped7.24.0
Upgrade to the patched version of Undici (and Node.js where applicable) that changes deduplication to stream response chunks as they arrive and prevents late deduplication when body streaming has started. Until patched, consider disabling the deduplication interceptor for untrusted endpoints or implementing request rate limiting.
undici 7.24.0 or later
- Identify the current undici version in your project by running 'npm list undici' or checking package.json
- Upgrade undici to version 7.24.0 or later using 'npm install undici@^7.24.0' or 'npm install undici@latest'
- Verify the upgrade was successful by running 'npm list undici' to confirm the installed version
- Test your application to ensure the deduplication interceptor functions correctly with the updated library
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Undici
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 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 $1,936.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-2581 — 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-2026-2581 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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