Media

UAParser.js: Unbounded `Sec-CH-UA-Model` parsing can trigger ReDoS in `withClientHints()`

Publicada: 15.06.2026
Actualizado: 11.10.2026 10:22

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

Regular expression Denial of Service - ReDoS (OWASP)

Credits

Thanks to @sondt99, who first reported the issue.

Software afectado

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Plataforma	Paquete	Versiones vulnerables	Corregida en
Paquete de npm	ua-parser-js	>= 2.0.1, < 2.0.10	2.0.10

Referencias

Puntuación CVSS 5.3/10

Vector CVSS: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Debilidad (CWE): CWE-1333, CWE-400
Plataforma: npm
Paquete: ua-parser-js
Publicada: 15.06.2026
Actualizado: 11.10.2026 10:22

Fuentes y licencias

OSV / GitHub Advisory Database - GHSA-9h5v-pfqq-x599 - CC BY 4.0

Historial de vulnerabilidades: ua-parser-js

Todas las vulnerabilidades publicadas de este paquete (Paquete de npm), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.

Entradas en total: 6
Primera → última: 05.2021 06.2026
Sin corrección: 0
Explotada en ataques: 0

Distribución por gravedad

Alta 5
Media 1

Divulgaciones por año

2021: 3
2022: 1
2023: 1
2024: 0
2025: 0
2026: 1

15.06.2026

UAParser.js: Unbounded `Sec-CH-UA-Model` parsing can trigger ReDoS in `withClientHints()` esta entrada

Media · 5.3 CVE-2026-48125 >= 2.0.1, < 2.0.10 2.0.10
24.01.2023

ReDoS Vulnerability in ua-parser-js version

Alta · 7.5 CVE-2022-25927 >= 0.7.30, < 0.7.33, >= 0.8.0, < 1.0.33 0.7.33, 1.0.33
09.02.2022

ua-parser-js Regular Expression Denial of Service vulnerability

Alta · 7.5 CVE-2020-7793 < 0.7.23 0.7.23
22.10.2021

Embedded malware in ua-parser-js

Alta · 8.8 CVE-2021-4229 >= 0.7.29, < 0.7.30, >= 0.8.0, < 0.8.1, >= 1.0.0, < 1.0.1 0.7.30, 0.8.1, 1.0.1
07.05.2021

Regular Expression Denial of Service in ua-parser-js

Alta · 7.5 CVE-2020-7733 < 0.7.22 0.7.22
06.05.2021

Regular Expression Denial of Service (ReDoS) in ua-parser-js

Alta · 7.5 CVE-2021-27292 >= 0.7.14, < 0.7.24 0.7.24

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