CVE-2026-2581: Undici Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-phc3-fgpg-7m6h
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CVSS 5.9
CWE-770
Published
Advisory Summary

CVE-2026-2581 is a MODERATE (CVSS 5.9) denial of service vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Undici libraries in the npm ecosystem. The issue involves undici has unbounded memory consumption in its deduplicationhandler via response buffering that leads to dos. Remediation is available by upgrading affected packages to version 7.24.0.

CVE-2026-2581 at a Glance

CVE Identifier CVE-2026-2581
GHSA Identifier GHSA-phc3-fgpg-7m6h
Severity MODERATE
CVSS v3.1 Base Score 5.9
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product Undici
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-2581

To remediate this vulnerability, upgrade all affected Undici dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

undici fixed: 7.24.0 
npm install undici@7.24.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls undici

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-2581, inspect your project dependencies using npm:

npm ls undici

Analyze the terminal output to locate any version of Undici in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 7.24.0), your application is affected.

Note: The npm ls undici command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In Undici, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Impact This 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. ## Patches The 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. ## Workarounds If upgrading immediately is not possible: - Disable `interceptors.deduplicate()` for affected clients/routes. - Use `skipHeaderNames` with a marker header to force high-risk requests to bypass deduplication. - Avoid concurrent identical requests to untrusted endpoints that may return very large/chunked bodies. - Apply upstream/proxy response-size and timeout limits.

CVE-2026-2581 Affected Undici Versions

1 component(s)
Fixed Versions:
7.24.0
Product / Package Ecosystem Affected Versions Fixed Version
undici
npm/undici
npm
≥ 7.17.0
< 7.24.0
7.24.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nodejs/undici/security/advisories/GHSA-phc3-fgpg-7m6h
NVD — CVE-2026-2581 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-2581
hackerone.com/reports/3513473 WEB
https://hackerone.com/reports/3513473
Undici Security Information SECURITY
https://cna.openjsf.org/security-advisories.html
Undici Source Repository REPOSITORY
https://github.com/nodejs/undici

Frequently Asked Questions

What is CVE-2026-2581?
CVE-2026-2581 is a security vulnerability in Undici involving Undici has Unbounded Memory Consumption in its DeduplicationHandler via Response Buffering that leads to DoS under CWE-770: Allocation of Resources Without Limits or Throttling.
Which Undici versions are affected?
Affected versions include releases prior to 7.24.0 across affected packages: undici.
What version fixes CVE-2026-2581?
Upgrading to 7.24.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is undici affected?
Yes, undici is affected in releases prior to 7.24.0. Upgrade your dependency to 7.24.0 or later.
What is the CVSS score of CVE-2026-2581?
CVE-2026-2581 has a CVSS v3.1 base score of 5.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-2581?
CVE-2026-2581 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check npm dependencies for CVE-2026-2581?
Run the dependency tree command: 'npm ls undici'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-phc3-fgpg-7m6h",
  "modified" : "2026-03-13T20:37:58Z",
  "published" : "2026-03-13T20:37:58Z",
  "aliases" : [ "CVE-2026-2581" ],
  "summary" : "Undici has Unbounded Memory Consumption in its DeduplicationHandler via Response Buffering that leads to DoS",
  "details" : "## Impact\nThis is an uncontrolled resource consumption vulnerability (CWE-400) that can lead to Denial of Service (DoS).\n\nIn 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.\n\nImpacted users are applications that use Undici’s deduplication interceptor against endpoints that may produce large or long-lived response bodies.\n\n## Patches\n\nThe 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.\n\nUsers should upgrade to the first official Undici (and Node.js, where applicable) releases that include this patch.\n\n## Workarounds\nIf upgrading immediately is not possible:\n\n- Disable `interceptors.deduplicate()` for affected clients/routes.\n- Use `skipHeaderNames` with a marker header to force high-risk requests to bypass deduplication.\n- Avoid concurrent identical requests to untrusted endpoints that may return very large/chunked bodies.\n- Apply upstream/proxy response-size and timeout limits.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "undici"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.17.0"
      }, {
        "fixed" : "7.24.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nodejs/undici/security/advisories/GHSA-phc3-fgpg-7m6h"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-2581"
  }, {
    "type" : "WEB",
    "url" : "https://hackerone.com/reports/3513473"
  }, {
    "type" : "WEB",
    "url" : "https://cna.openjsf.org/security-advisories.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nodejs/undici"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-13T20:37:58Z",
    "nvd_published_at" : "2026-03-12T21:16:25Z"
  }
}