CVE-2026-84947: Undici Remote Code Execution Vulnerability

LOW
Advisory Identifier: GHSA-2gqq-gqf2-x968
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CVSS 3.7
CWE-20 CWE-248
Published
Advisory Summary

CVE-2026-84947 is a LOW (CVSS 3.7) remote code execution vulnerability (CWE-20: Improper Input Validation) affecting Undici libraries in the npm ecosystem. The issue involves undici vulnerable to response truncation via oversized chunked responses in the dump interceptor. Remediation is available by upgrading affected packages to version 7.29.1, 8.10.2.

CVE-2026-84947 at a Glance

CVE Identifier CVE-2026-84947
GHSA Identifier GHSA-2gqq-gqf2-x968
Severity LOW
CVSS v3.1 Base Score 3.7
CWE Classification CWE-20: Improper Input Validation
Affected Product Undici
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 3.7

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:L/A:N).

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 Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-84947

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: 7.29.1 
npm install undici@7.29.1
undici fixed: 8.10.2 
npm install undici@8.10.2
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-2026-84947, 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 7.29.1), 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-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. 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 undici's `interceptors.dump()` reads and discards response bodies up to a configurable `maxSize`. When a response declares a `Content-Length` that exceeds `maxSize`, the request is aborted cleanly. When a response is sent chunked (no `Content-Length`) and its body exceeds `maxSize`, it is not aborted: the interceptor ends the response early once the accumulated size reaches `maxSize`, and continued delivery from the parser triggers an internal assertion that is caught and turned into a request abort and connection tear-down. The application observes a misleading `200` with an empty or truncated body while the connection is disconnected. Any application using the dump interceptor against untrusted or misbehaving upstreams is affected. ### Patches Upgrade to `7.29.1` or `8.10.2`. The dump interceptor now enforces `maxSize` on both the declared and the received body size, aborting the request with a `RequestAbortedError` instead of returning a truncated response. ### Workarounds None. Avoid using `interceptors.dump()` with untrusted upstreams until upgraded.

CVE-2026-84947 Affected Undici Versions

2 component(s)
Fixed Versions:
7.29.18.10.2
Product / Package Ecosystem Affected Versions Fixed Version
undici
npm/undici
npm
≥ 7.1.0
< 7.29.1
7.29.1
undici
npm/undici
npm
≥ 8.0.0
< 8.10.2
8.10.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nodejs/undici/security/advisories/GHSA-2gqq-gqf2-x968
NVD — CVE-2026-84947 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-84947
Security Fix Commit FIX COMMIT
https://github.com/nodejs/undici/commit/21693f406f0142f3504192e9f9b022dcf84782ae
Security Fix Commit FIX COMMIT
https://github.com/nodejs/undici/commit/6d583124e7cf60b640097d64144ed633cc450584
Undici Security Information SECURITY
https://cna.openjsf.org/security-advisories.html
Undici Source Repository REPOSITORY
https://github.com/nodejs/undici
Undici Release RELEASE
https://github.com/nodejs/undici/releases/tag/v7.29.1
Undici Release RELEASE
https://github.com/nodejs/undici/releases/tag/v8.10.2

Frequently Asked Questions

What is CVE-2026-84947?
CVE-2026-84947 is a security vulnerability in Undici involving undici vulnerable to response truncation via oversized chunked responses in the dump interceptor under CWE-20: Improper Input Validation.
Which Undici versions are affected?
Affected versions include releases prior to 7.29.1, 8.10.2 across affected packages: undici.
What version fixes CVE-2026-84947?
Upgrading to 7.29.1, 8.10.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is undici affected?
Yes, undici is affected in releases prior to 7.29.1, 8.10.2. Upgrade your dependency to 7.29.1, 8.10.2 or later.
What is the CVSS score of CVE-2026-84947?
CVE-2026-84947 has a CVSS v3.1 base score of 3.7 (LOW) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2026-84947?
CVE-2026-84947 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check npm dependencies for CVE-2026-84947?
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-2gqq-gqf2-x968",
  "modified" : "2026-09-29T18:18:51Z",
  "published" : "2026-09-29T18:18:51Z",
  "aliases" : [ "CVE-2026-84947" ],
  "summary" : "undici vulnerable to response truncation via oversized chunked responses in the dump interceptor",
  "details" : "### Impact\n\nundici's `interceptors.dump()` reads and discards response bodies up to a configurable `maxSize`. When a response declares a `Content-Length` that exceeds `maxSize`, the request is aborted cleanly. When a response is sent chunked (no `Content-Length`) and its body exceeds `maxSize`, it is not aborted: the interceptor ends the response early once the accumulated size reaches `maxSize`, and continued delivery from the parser triggers an internal assertion that is caught and turned into a request abort and connection tear-down. The application observes a misleading `200` with an empty or truncated body while the connection is disconnected. Any application using the dump interceptor against untrusted or misbehaving upstreams is affected.\n\n### Patches\n\nUpgrade to `7.29.1` or `8.10.2`. The dump interceptor now enforces `maxSize` on both the declared and the received body size, aborting the request with a `RequestAbortedError` instead of returning a truncated response.\n\n### Workarounds\n\nNone. Avoid using `interceptors.dump()` with untrusted upstreams until upgraded.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "undici"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.1.0"
      }, {
        "fixed" : "7.29.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "undici"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0.0"
      }, {
        "fixed" : "8.10.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nodejs/undici/security/advisories/GHSA-2gqq-gqf2-x968"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-84947"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nodejs/undici/commit/21693f406f0142f3504192e9f9b022dcf84782ae"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nodejs/undici/commit/6d583124e7cf60b640097d64144ed633cc450584"
  }, {
    "type" : "WEB",
    "url" : "https://cna.openjsf.org/security-advisories.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nodejs/undici"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nodejs/undici/releases/tag/v7.29.1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nodejs/undici/releases/tag/v8.10.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-248" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-29T18:18:51Z",
    "nvd_published_at" : "2026-09-04T17:17:02Z"
  }
}