CVE-2026-32141: Flatted Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-25h7-pfq9-p65f
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CVSS 7.5
CWE-674
Published
Advisory Summary

CVE-2026-32141 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-674: Uncontrolled Recursion) affecting Flatted libraries in the npm ecosystem. The issue involves flatted vulnerable to unbounded recursion dos in parse() revive phase. Remediation is available by upgrading affected packages to version 3.4.0.

CVE-2026-32141 at a Glance

CVE Identifier CVE-2026-32141
GHSA Identifier GHSA-25h7-pfq9-p65f
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-674: Uncontrolled Recursion
Affected Product Flatted
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

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

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
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-2026-32141

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

flatted fixed: 3.4.0 
npm install flatted@3.4.0
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 flatted

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-32141, inspect your project dependencies using npm:

npm ls flatted

Analyze the terminal output to locate any version of Flatted in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.4.0), your application is affected.

Note: The npm ls flatted 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-674: Uncontrolled Recursion, where the product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. In Flatted, 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

## Summary flatted's `parse()` function uses a recursive `revive()` phase to resolve circular references in deserialized JSON. When given a crafted payload with deeply nested or self-referential `$` indices, the recursion depth is unbounded, causing a stack overflow that crashes the Node.js process. ## Impact Denial of Service (DoS). Any application that passes untrusted input to `flatted.parse()` can be crashed by an unauthenticated attacker with a single request. flatted has ~87M weekly npm downloads and is used as the circular-JSON serialization layer in many caching and logging libraries. ## Proof of Concept ```javascript const flatted = require('flatted'); // Build deeply nested circular reference chain const depth = 20000; const arr = new Array(depth + 1); arr[0] = '{"a":"1"}'; for (let i = 1; i <= depth; i++) { arr[i] = `{"a":"${i + 1}"}`; } arr[depth] = '{"a":"leaf"}'; const payload = JSON.stringify(arr); flatted.parse(payload); // RangeError: Maximum call stack size exceeded ``` ## Fix The maintainer has already merged an iterative (non-recursive) implementation in PR #88, converting the recursive `revive()` to a stack-based loop. ## Affected Versions All versions prior to the PR #88 fix.

CVE-2026-32141 Affected Flatted Versions

1 component(s)
Fixed Versions:
3.4.0
Product / Package Ecosystem Affected Versions Fixed Version
flatted
npm/flatted
npm
< 3.4.0
3.4.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/WebReflection/flatted/security/advisories/GHSA-25h7-pfq9-p65f
NVD — CVE-2026-32141 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-32141
Flatted Source Repository REPOSITORY
https://github.com/WebReflection/flatted/pull/88
Security Fix Commit FIX COMMIT
https://github.com/WebReflection/flatted/commit/7eb65d857e1a40de11c47461cdbc8541449f0606
Flatted Source Repository REPOSITORY
https://github.com/WebReflection/flatted

Frequently Asked Questions

What is CVE-2026-32141?
CVE-2026-32141 is a security vulnerability in Flatted involving flatted vulnerable to unbounded recursion DoS in parse() revive phase under CWE-674: Uncontrolled Recursion.
Which Flatted versions are affected?
Affected versions include releases prior to 3.4.0 across affected packages: flatted.
What version fixes CVE-2026-32141?
Upgrading to 3.4.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is flatted affected?
Yes, flatted is affected in releases prior to 3.4.0. Upgrade your dependency to 3.4.0 or later.
What is the CVSS score of CVE-2026-32141?
CVE-2026-32141 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-32141?
CVE-2026-32141 is classified under CWE-674: Uncontrolled Recursion (The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.).
How can I check npm dependencies for CVE-2026-32141?
Run the dependency tree command: 'npm ls flatted'. 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-25h7-pfq9-p65f",
  "modified" : "2026-03-13T15:40:42Z",
  "published" : "2026-03-13T15:40:42Z",
  "aliases" : [ "CVE-2026-32141" ],
  "summary" : "flatted vulnerable to unbounded recursion DoS in parse() revive phase",
  "details" : "## Summary\n\nflatted's `parse()` function uses a recursive `revive()` phase to resolve circular references in deserialized JSON. When given a crafted payload with deeply nested or self-referential `$` indices, the recursion depth is unbounded, causing a stack overflow that crashes the Node.js process.\n\n## Impact\n\nDenial of Service (DoS). Any application that passes untrusted input to `flatted.parse()` can be crashed by an unauthenticated attacker with a single request.\n\nflatted has ~87M weekly npm downloads and is used as the circular-JSON serialization layer in many caching and logging libraries.\n\n## Proof of Concept\n\n```javascript\nconst flatted = require('flatted');\n\n// Build deeply nested circular reference chain\nconst depth = 20000;\nconst arr = new Array(depth + 1);\narr[0] = '{\"a\":\"1\"}';\nfor (let i = 1; i <= depth; i++) {\n  arr[i] = `{\"a\":\"${i + 1}\"}`;\n}\narr[depth] = '{\"a\":\"leaf\"}';\n\nconst payload = JSON.stringify(arr);\nflatted.parse(payload); // RangeError: Maximum call stack size exceeded\n```\n\n## Fix\n\nThe maintainer has already merged an iterative (non-recursive) implementation in PR #88, converting the recursive `revive()` to a stack-based loop.\n\n## Affected Versions\n\nAll versions prior to the PR #88 fix.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "flatted"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.4.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/WebReflection/flatted/security/advisories/GHSA-25h7-pfq9-p65f"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-32141"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/WebReflection/flatted/pull/88"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/WebReflection/flatted/commit/7eb65d857e1a40de11c47461cdbc8541449f0606"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/WebReflection/flatted"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-674" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-13T15:40:42Z",
    "nvd_published_at" : "2026-03-12T18:16:25Z"
  }
}