GHSA-9h5v-pfqq-x599 — ua-parser-js
MEDIUMGHSA-9h5v-pfqq-x599 is a medium-severity (CVSS 5.3) Uncontrolled Resource Consumption vulnerability in ua-parser-js. A fix is available for ua-parser-js — see the affected versions and patch details below.
UAParser.js: Unbounded `Sec-CH-UA-Model` parsing can trigger ReDoS in `withClientHints()`
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-9h5v-pfqq-x599.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-9h5v-pfqq-x599 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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.
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 | 2.0.10npm install ua-parser-js@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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-9h5v-pfqq-x599 can be triaged on real exposure rather than presence alone.
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 Security finds GHSA-9h5v-pfqq-x599 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.