CVE-2021-4250: 
Ruby vulnerability analysis and mitigation

A vulnerability was identified in cgriego activeattr up to version 0.15.2, affecting the function call in the lib/activeattr/typecasting/boolean_typecaster.rb file of the Regex Handler component. The vulnerability was discovered and disclosed in December 2022, and it was assigned CVE-2021-4250. The issue was classified as problematic and could lead to denial of service conditions (CVE MITRE).

The vulnerability stems from a Regular Expression Denial of Service (ReDoS) issue in the BooleanTypecaster#call method. The problematic regular expression /\A[-+]?(0+.?0*|0*.?0+)\z/ could be exploited with specially crafted input strings, such as a large number of '0' characters followed by a non-matching character, causing excessive processing time (GitHub Issue).

When exploited, this vulnerability can lead to denial of service conditions by causing the application to spend excessive time processing specially crafted input strings, potentially affecting system availability (CVE MITRE).

The vulnerability was addressed in version 0.15.3 of activeattr through the implementation of possessive quantifiers in the regular expression pattern. Users are recommended to upgrade to version 0.15.3 or later to resolve this security issue. The fix was implemented through patch dab95e5843b01525444b82bd7b336ef1d79377df ([GitHub Commit](https://github.com/cgriego/activeattr/commit/dab95e5843b01525444b82bd7b336ef1d79377df)).