CVE-2021-4305: 
JavaScript vulnerability analysis and mitigation

A vulnerability was discovered in Woorank robots-txt-guard affecting the makePathPattern function in lib/patterns.js. The vulnerability (CVE-2021-4305) relates to inefficient regular expression complexity, where manipulation of the pattern argument could lead to potential issues. The vulnerability was publicly disclosed and has been assigned a CVSS 3.1 base score of 7.5 (HIGH) by NVD (NVD).

The vulnerability stems from the way the makePathPattern function handles pattern splitting, which could result in inefficient regular expression complexity. The issue specifically occurs when processing patterns with multiple asterisks, which could be transformed into resource-intensive regular expressions. The vulnerability has been assigned CWE-1333 (Inefficient Regular Expression Complexity). The CVSS vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (NVD).

When exploited, the vulnerability could lead to performance issues due to inefficient regular expression processing. For example, a pattern like '/*.js$' would be transformed into a complex regex that takes seconds to execute, whereas a simpler pattern could achieve the same result more efficiently (GitHub PR).

A patch has been released with commit ID c03827cd2f9933619c23894ce7c98401ea824020. The fix involves modifying the pattern splitting mechanism to use '/*+/' instead of '*', preventing the creation of inefficient regular expressions. It is recommended to update to version 1.0.0 or later of the robots-txt-guard package (GitHub Commit).