MooTools is a collection of JavaScript utilities for JavaScript developers. All known versions include a CSS selector parser that is vulnerable to Regular Expression Denial of Service (ReDoS). An attack requires that an attacker can inject a string into a CSS selector at runtime, which is quite common with e.g. jQuery CSS selectors. No patches are available for this issue.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-32821
• https://securitylab.github.com/advisories/GHSL-2020-345-redos-mootools