GHSA-9h5v-pfqq-x599 UAParser.js: Unbounded `Sec-CH-UA-Model` parsing can trigger ReDoS in `withClientHints()`

• npm ua-parser-js: >= 2.0.1, < 2.0.10 → fixed in 2.0.10

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: ```js / ([\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 ```js 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 • Regular expression Denial of Service - ReDoS (OWASP) Credits Thanks to @sondt99, who first reported the issue.