CVE-2020-26302

Vulnerability

Description

is.js, a general-purpose check library, includes a regular expression to validate URLs that was copied from a gist. This regex is vulnerable to Regular Expression Denial of Service (ReDoS) due to exponential backtracking on crafted input. Versions 0.9.0 and prior are affected [1][2].

Exploitation

An attacker can exploit this vulnerability by providing a maliciously crafted URL string to any application using is.js for input validation. When the regex processes this string, it may enter a state of near-infinite backtracking, consuming excessive CPU resources. No authentication or special network position is required if the application exposes the validation to untrusted input [2].

Impact

Successful exploitation leads to a denial of service condition, exhausting server resources and potentially causing the application to become unresponsive. This can be used to disrupt services that rely on is.js for URL checking [1][2].

Mitigation

As of the disclosure timeline, the project maintainer did not respond, and no patch has been released. Users are advised to replace the vulnerable regex with a safer alternative or avoid using is.js for URL validation in security-critical contexts [2][4].