CVE-2026-25224: Fastify Denial of Service Vulnerability

LOW
Advisory Identifier: GHSA-mrq3-vjjr-p77c
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CVSS 3.7
CWE-770
Published
Advisory Summary

CVE-2026-25224 is a LOW (CVSS 3.7) denial of service vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Fastify libraries in the npm ecosystem. The issue involves fastify vulnerable to dos via unbounded memory allocation in sendwebstream. Remediation is available by upgrading affected packages to version 5.7.3.

CVE-2026-25224 at a Glance

CVE Identifier CVE-2026-25224
GHSA Identifier GHSA-mrq3-vjjr-p77c
Severity LOW
CVSS v3.1 Base Score 3.7
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product Fastify
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:N/A:L).

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 Low (A:L)

How to Fix CVE-2026-25224

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

fastify fixed: 5.7.3 
npm install fastify@5.7.3
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 fastify

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-25224, inspect your project dependencies using npm:

npm ls fastify

Analyze the terminal output to locate any version of Fastify in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.7.3), your application is affected.

Note: The npm ls fastify 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 Fastify, 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 A Denial of Service vulnerability in Fastify’s Web Streams response handling can allow a remote client to exhaust server memory. Applications that return a `ReadableStream` (or `Response` with a Web Stream body) via `reply.send()` are impacted. A slow or non-reading client can trigger unbounded buffering when backpressure is ignored, leading to process crashes or severe degradation. ### Patches The issue is fixed in Fastify 5.7.3. Users should upgrade to 5.7.3 or later. ### Workarounds Avoid sending Web Streams from Fastify responses (e.g., `ReadableStream` or `Response` bodies). Use Node.js streams (`stream.Readable`) or buffered payloads instead until the project can upgrade. ### References - https://hackerone.com/reports/3524779

CVE-2026-25224 Affected Fastify Versions

1 component(s)
Fixed Versions:
5.7.3
Product / Package Ecosystem Affected Versions Fixed Version
fastify
npm/fastify
npm
< 5.7.3
5.7.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/fastify/fastify/security/advisories/GHSA-mrq3-vjjr-p77c
NVD — CVE-2026-25224 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-25224
Security Fix Commit FIX COMMIT
https://github.com/fastify/fastify/commit/eb11156396f6a5fedaceed0140aed2b7f026be37
hackerone.com/reports/3524779 WEB
https://hackerone.com/reports/3524779
Fastify Source Repository REPOSITORY
https://github.com/fastify/fastify

Frequently Asked Questions

What is CVE-2026-25224?
CVE-2026-25224 is a security vulnerability in Fastify involving Fastify Vulnerable to DoS via Unbounded Memory Allocation in sendWebStream under CWE-770: Allocation of Resources Without Limits or Throttling.
Which Fastify versions are affected?
Affected versions include releases prior to 5.7.3 across affected packages: fastify.
What version fixes CVE-2026-25224?
Upgrading to 5.7.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is fastify affected?
Yes, fastify is affected in releases prior to 5.7.3. Upgrade your dependency to 5.7.3 or later.
What is the CVSS score of CVE-2026-25224?
CVE-2026-25224 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:N/A:L.
What CWE is associated with CVE-2026-25224?
CVE-2026-25224 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-2026-25224?
Run the dependency tree command: 'npm ls fastify'. 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-mrq3-vjjr-p77c",
  "modified" : "2026-02-04T17:46:06Z",
  "published" : "2026-02-02T22:25:05Z",
  "aliases" : [ "CVE-2026-25224" ],
  "summary" : "Fastify Vulnerable to DoS via Unbounded Memory Allocation in sendWebStream",
  "details" : "### Impact\nA Denial of Service vulnerability in Fastify’s Web Streams response handling can allow a remote client to exhaust server memory. Applications that return a `ReadableStream` (or `Response` with a Web Stream body) via `reply.send()` are impacted. A slow or non-reading client can trigger unbounded buffering when backpressure is ignored, leading to process crashes or severe degradation.\n\n### Patches\nThe issue is fixed in Fastify 5.7.3. Users should upgrade to 5.7.3 or later.\n\n### Workarounds\nAvoid sending Web Streams from Fastify responses (e.g., `ReadableStream` or `Response` bodies). Use Node.js streams (`stream.Readable`) or buffered payloads instead until the project can upgrade.\n\n### References\n- https://hackerone.com/reports/3524779",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "fastify"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.7.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.7.2"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/fastify/fastify/security/advisories/GHSA-mrq3-vjjr-p77c"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-25224"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/fastify/fastify/commit/eb11156396f6a5fedaceed0140aed2b7f026be37"
  }, {
    "type" : "WEB",
    "url" : "https://hackerone.com/reports/3524779"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/fastify/fastify"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-02T22:25:05Z",
    "nvd_published_at" : "2026-02-03T22:16:31Z"
  }
}