The validators package 0.12.2 through 0.12.5 for Python enters an infinite loop when validators.domain is called with a crafted domain string. This is fixed in 0.12.6.

Torbot is an open source tor network intelligence tool. In affected versions the `torbot.modules.validators.validate_link function` uses the python-validators URL validation regex. This particular regular expression has an exponential complexity which allows an attacker to cause an application crash using a well-crafted argument. An attacker can use a well-crafted URL argument to exploit the vulnerability in the regular expression and cause a Denial of Service on the system. The validators file has been removed in version 4.0.0. Users are advised to upgrade. There are no known workarounds for this vulnerability.