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The vulnerability (CVE-2026-?????) in the `seroval` JavaScript serialization/deserialization library stems from improper validation of object keys during the parsing of JSON strings. When `seroval` deserializes a maliciously crafted JSON object, it fails to sanitize keys containing special characters like __proto__, constructor, or prototype. This allows an attacker to inject properties into the global Object prototype. During the deserialization process, the library’s key assignment logic uses paths like `obj
= value` without checking if `key` is a dangerous prototype property. Consequently, for every object created after pollution, the injected properties are inherited, potentially altering the application's behavior, leading to remote code execution (RCE) via subsequent gadget chains, or causing denial of service (DoS). Platform: seroval (JavaScript) Version: < v1.0.3 Vulnerability: Prototype Pollution Severity: Critical date: 2026-01-21 <h2 style="color: blue;">Prediction: Patch 2026-01-28</h2> <h2 style="color: blue;">What Undercode Say:</h2> [bash] npm ls seroval cat payload.json
const payload = <code>{"__proto__":{"polluted":"yes"}}</code>;
const deserialized = seroval.deserialize(payload);
console.log({}.polluted); // 'yes'
How Exploit:
fetch('/api/parse', {
method: 'POST',
body: '{"<strong>proto</strong>":{"admin":true}}'
});
Protection from this CVE
Upgrade to `seroval@^1.0.3`.
Implement input sanitization.
Use `Object.create(null)`.
Impact:
Remote Code Execution
Authorization Bypass
Application Crash
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Sources:
Reported By: github.com
Extra Source Hub:
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