{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.1.3"
      },
      "package": {
        "ecosystem": "npm",
        "name": "mojic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.1.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-208"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-16T21:10:17Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\nThe `CipherEngine` in Mojic v2.1.3 uses a standard equality operator (`!==`) to verify the HMAC-SHA256 integrity seal during the decryption phase. This creates an Observable Timing Discrepancy (CWE-208), allowing a potential attacker to bypass the file integrity check via a timing attack.\n\n### Details\nIn `lib/CipherEngine.js`, the footer check validates the HMAC signature using a standard string comparison:\n`if (footerHex !== calcDigest) { ... }`\n\nStandard string comparisons in JavaScript short-circuit; they return `false` the moment a character mismatch occurs. Because the time taken to evaluate the comparison is proportional to the number of matching leading bytes, an attacker can measure the exact microseconds it takes for the engine to throw the `FILE_TAMPERED` error. By repeatedly altering the signature byte-by-byte and analyzing these minute timing differences, a malicious actor can theoretically forge a valid HMAC signature without possessing the decryption password.\n\n### PoC\nThe vulnerable implementation is located in `lib/CipherEngine.js`, within the `getDecryptStream()` flush method (approximately line 265):\n\n```javascript\n// Vulnerable Code\nif (footerHex !== calcDigest) {\n    this.emit(\u0027error\u0027, new Error(\"FILE_TAMPERED\"));\n    return;\n}\n```\n\n### Recommended Remediation:\nReplace the standard equality operator with Node.js\u0027s built-in constant-time comparison utility, crypto.timingSafeEqual().\n\n```JavaScript\n// Remediated Code\nconst footerBuffer = Buffer.from(footerHex, \u0027hex\u0027);\nconst calcBuffer = Buffer.from(calcDigest, \u0027hex\u0027);\n\nif (footerBuffer.length !== calcBuffer.length || !crypto.timingSafeEqual(footerBuffer, calcBuffer)) {\n    this.emit(\u0027error\u0027, new Error(\"FILE_TAMPERED\"));\n    return;\n}\n```\n\n### Impact\nIf successfully exploited, an attacker could tamper with the encrypted .mojic payload and forge a valid HMAC signature. This bypasses the integrity seal, tricking the decryption engine into processing maliciously injected emoji streams. Because the engine translates these emojis back into C keywords and raw data chunks, this could ultimately result in arbitrary Code Injection into the restored .c source code when an unsuspecting user decrypts the tampered file.",
  "id": "GHSA-wqq3-wfmp-v85g",
  "modified": "2026-04-16T21:10:17Z",
  "published": "2026-04-16T21:10:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/notamitgamer/mojic/security/advisories/GHSA-wqq3-wfmp-v85g"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/notamitgamer/mojic"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mojic: Observable Timing Discrepancy in HMAC Verification"
}