CVE-2026-12644: ts-deepmerge Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-87mf-gv2c-c62c
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CVSS 5.3
CWE-248
Published
Advisory Summary

CVE-2026-12644 is a MODERATE (CVSS 5.3) denial of service vulnerability (CWE-248: Uncaught Exception) affecting ts-deepmerge libraries in the npm ecosystem. The issue involves prototype method override leads to dos. Remediation is available by upgrading affected packages to version 8.0.0.

CVE-2026-12644 at a Glance

CVE Identifier CVE-2026-12644
GHSA Identifier GHSA-87mf-gv2c-c62c
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-248: Uncaught Exception
Affected Product ts-deepmerge
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.3

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:L).

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 Low (A:L)

How to Fix CVE-2026-12644

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

ts-deepmerge fixed: 8.0.0 
npm install ts-deepmerge@8.0.0
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 ts-deepmerge

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-12644, inspect your project dependencies using npm:

npm ls ts-deepmerge

Analyze the terminal output to locate any version of ts-deepmerge in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 8.0.0), your application is affected.

Note: The npm ls ts-deepmerge 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-248: Uncaught Exception, where an exception is thrown from a function, but it is not caught. In ts-deepmerge, 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

Versions of the package ts-deepmerge before 8.0.0 are vulnerable to Uncaught Exception due to the improper handling of built-in Object.prototype methods (such as toString, valueOf). When user-controlled input contains these keys with non-function values, the resulting merged object becomes broken — any string context operation throws a TypeError, crashing the application.

CVE-2026-12644 Affected ts-deepmerge Versions

1 component(s)
Fixed Versions:
8.0.0
Product / Package Ecosystem Affected Versions Fixed Version
ts-deepmerge
npm/ts-deepmerge
npm
< 8.0.0
8.0.0

References

NVD — CVE-2026-12644 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-12644
Security Fix Commit FIX COMMIT
https://github.com/voodoocreation/ts-deepmerge/commit/305a05831a462fb2c353d3cbbff55a0733286f8c
ts-deepmerge Source Repository REPOSITORY
https://gist.github.com/igorg1312/775fa00114c4d47df6ae0551779ab407
ts-deepmerge Source Repository REPOSITORY
https://github.com/voodoocreation/ts-deepmerge
ts-deepmerge Security Information SECURITY
https://security.snyk.io/vuln/SNYK-JS-TSDEEPMERGE-17339141

Frequently Asked Questions

What is CVE-2026-12644?
CVE-2026-12644 is a security vulnerability in ts-deepmerge involving Prototype Method Override leads to DoS under CWE-248: Uncaught Exception.
Which ts-deepmerge versions are affected?
Affected versions include releases prior to 8.0.0 across affected packages: ts-deepmerge.
What version fixes CVE-2026-12644?
Upgrading to 8.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is ts-deepmerge affected?
Yes, ts-deepmerge is affected in releases prior to 8.0.0. Upgrade your dependency to 8.0.0 or later.
What is the CVSS score of CVE-2026-12644?
CVE-2026-12644 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2026-12644?
CVE-2026-12644 is classified under CWE-248: Uncaught Exception (An exception is thrown from a function, but it is not caught.).
How can I check npm dependencies for CVE-2026-12644?
Run the dependency tree command: 'npm ls ts-deepmerge'. 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-87mf-gv2c-c62c",
  "modified" : "2026-06-19T21:41:52Z",
  "published" : "2026-06-19T06:31:56Z",
  "aliases" : [ "CVE-2026-12644" ],
  "summary" : "ts-deepmerge: Prototype Method Override leads to DoS",
  "details" : "Versions of the package ts-deepmerge before 8.0.0 are vulnerable to Uncaught Exception due to the improper handling of built-in Object.prototype methods (such as toString, valueOf). When user-controlled input contains these keys with non-function values, the resulting merged object becomes broken — any string context operation throws a TypeError, crashing the application.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "ts-deepmerge"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "8.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-12644"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/voodoocreation/ts-deepmerge/commit/305a05831a462fb2c353d3cbbff55a0733286f8c"
  }, {
    "type" : "WEB",
    "url" : "https://gist.github.com/igorg1312/775fa00114c4d47df6ae0551779ab407"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/voodoocreation/ts-deepmerge"
  }, {
    "type" : "WEB",
    "url" : "https://security.snyk.io/vuln/SNYK-JS-TSDEEPMERGE-17339141"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-248" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T21:41:52Z",
    "nvd_published_at" : "2026-06-19T06:17:01Z"
  }
}