CVE-2026-25047: deepHas npm Prototype Pollution Flaw

CVE-2026-25047 Overview

A critical prototype pollution vulnerability has been identified in the deephas npm package, a utility library that provides a test for the existence of nested object keys and optionally returns that key. This vulnerability exists in version 1.0.7 of the package and allows an attacker to modify global object behavior through prototype pollution.

Prototype pollution is a JavaScript-specific vulnerability that enables attackers to inject properties into existing JavaScript object prototypes. When exploited, this can lead to widespread application compromise, as polluted properties become accessible to all objects inheriting from the affected prototype.

Critical Impact

Attackers can manipulate the global Object prototype, potentially leading to remote code execution, denial of service, or authentication bypass depending on how the application uses the affected library.

Affected Products

• deephas npm package version 1.0.7

Discovery Timeline

• 2026-01-29 - CVE CVE-2026-25047 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-25047

Vulnerability Analysis

The prototype pollution vulnerability in deephas version 1.0.7 occurs due to insufficient input validation when processing nested object key paths. The library failed to properly sanitize user-controlled input, specifically allowing the __proto__ property to be accessed and modified through the key path string. This is classified under CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes).

When an attacker provides a malicious string containing __proto__ as part of the key path, they can inject arbitrary properties into the base Object prototype. These injected properties then propagate to all objects in the JavaScript runtime that inherit from Object.prototype, which includes virtually every object in a typical Node.js application.

Root Cause

The root cause of this vulnerability lies in the string parsing logic used to traverse nested object paths. The original implementation used JavaScript's native split('.') method to parse dot-separated key paths without validating whether any segment of the path references the __proto__ property. This oversight allowed attackers to craft malicious input strings that could traverse and pollute the prototype chain.

Attack Vector

The attack vector requires local access, where an attacker can provide specially crafted input to the deephas functions. By passing a string containing __proto__ segments in the key path, an attacker can inject malicious properties into the global Object prototype. This pollution can then be leveraged to:

1. Override application configuration values
2. Bypass security checks that rely on property existence
3. Inject malicious functions or values that get executed elsewhere in the application
4. Cause denial of service by corrupting critical object properties

The following patch demonstrates how the vulnerability was addressed in version 1.0.8:

 
}
 
+function splitOnDot(str) {
+  var result = [];
+  var current = "";
+  var i = 0;
+
+  while (i < str.length) {
+    if (str[i] === ".") {
+      result[result.length] = current;
+      current = "";
+    } else {
+      current = current + str[i];
+    }
+    i = i + 1;
+  }
+
+  result[result.length] = current;
+  return result;
+}
+
function add(obj, str, val) {
    "use strict";
    try {
+        var items = splitOnDot(str);
        if (typeof str !== "string") {
            return;
        }
-        if (str.indexOf('__proto__') != -1) {

Source: GitHub Commit Update

Detection Methods for CVE-2026-25047

Indicators of Compromise

• Unexpected properties appearing on Object.prototype in your application
• Application behavior changes that suggest modified global object defaults
• Log entries showing access patterns with __proto__ or constructor.prototype in request parameters

Detection Strategies

• Audit your package.json and package-lock.json files for deephas version 1.0.7 or earlier
• Use npm audit or Snyk to scan for vulnerable dependency versions
• Implement runtime monitoring for Object.prototype modifications using Object.freeze() on critical prototypes
• Review application logs for suspicious input patterns containing prototype pollution markers

Monitoring Recommendations

• Monitor for unusual object property access patterns in application telemetry
• Set up alerts for dependency vulnerability notifications through npm or GitHub Dependabot
• Implement Content Security Policy headers to limit the impact of potential code injection

How to Mitigate CVE-2026-25047

Immediate Actions Required

• Upgrade the deephas npm package to version 1.0.8 or later immediately
• Run npm audit fix to automatically resolve vulnerable dependency versions
• Review application code for any direct usage of deephas functions with untrusted input
• Consider implementing input validation at the application layer as defense-in-depth

Patch Information

The vulnerability has been addressed in deephas version 1.0.8. The fix implements a custom string splitting function with proper validation to prevent prototype pollution. Detailed patch information is available in the GitHub Security Advisory GHSA-2733 and the GitHub Commit Update.

Workarounds

• If immediate upgrade is not possible, implement input sanitization to filter out __proto__, constructor, and prototype from user-controlled key paths
• Use Object.freeze(Object.prototype) early in application initialization to prevent prototype modifications
• Consider replacing deephas with alternative libraries that have built-in prototype pollution protection

# Configuration example
# Upgrade deephas to patched version
npm update deephas

# Verify installed version
npm list deephas

# Run security audit
npm audit