GHSA-9h5v-pfqq-x599
MEDIUMGHSA-9h5v-pfqq-x599 is a medium-severity (CVSS 5.3) Uncontrolled Resource Consumption vulnerability in ua-parser-js. O3 Security confirms whether GHSA-9h5v-pfqq-x599 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
UAParser.js: Unbounded `Sec-CH-UA-Model` parsing can trigger ReDoS in `withClientHints()`
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
ua-parser-jsnpmDescription
Summary
A regular expression denial-of-service (ReDoS) vulnerability has been discovered in ua-parser-js when using the Client Hints API. By sending a crafted Sec-CH-UA-Model header to an application that calls UAParser(headers).withClientHints(), an attacker can cause the parser to spend excessive CPU time due to catastrophic backtracking in the device regex:
/ ([\w ]+) miui\/v?\d/i
Unlike when using the User-Agent value, which has a hard limit of UA_MAX_LENGTH = 500, when using Client Hints, values are copied without a length limit before being passed into regex parsing.
PoC
const { UAParser } = require('ua-parser-js');
const headers = {
'sec-ch-ua-platform': '"Android"',
'sec-ch-ua-mobile': '?1',
'sec-ch-ua-model': '"' + 'A '.repeat(25000) + '"'
};
const t0 = process.hrtime.bigint();
UAParser(headers).withClientHints();
const ms = Number(process.hrtime.bigint() - t0) / 1e6;
if (ms > 100) {
console.log('Potential ReDoS');
}
Impact
This vulnerability allows an unauthenticated attacker to trigger a denial-of-service condition in any server-side application that uses UAParser(headers).withClientHints(). A single request with a ~32,000-character model value can consume over 400ms of CPU time, with parsing time growing polynomially with input length. The impact is availability only, there is no confidentiality or integrity impact.
Affected Versions
ua-parser-js versions >=2.0.1, <=2.0.9 are affected. The withClientHints() API is not present in version 0.7.x or 1.x.
Patches
A patch has been released to fix the vulnerable regular expression and limit the Client Hints input. Users should update to version 2.0.10 or later.
References
Credits
Thanks to @sondt99, who first reported the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | ua-parser-js | ≥ 2.0.1&&< 2.0.10 | 2.0.10 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ua-parser-js. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update ua-parser-js to 2.0.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9h5v-pfqq-x599 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 pinpoints whether GHSA-9h5v-pfqq-x599 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-9h5v-pfqq-x599. 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-9h5v-pfqq-x599 in your dependencies?
O3 detects GHSA-9h5v-pfqq-x599 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.