String::Util versions before 1.36 for Perl are susceptible to a regular expression denial of service. The trim and rtrim functions stripped trailing whitespace with s/\s*$//u. Because \s* matches greedily and the $ anchor fails whenever a non-whitespace character follows the whitespace, the regex engine retries the match at each offset of a long whitespace run, producing quadratic backtracking. The fix replaces \s*$ with \s+$. Any caller that passes untrusted input to trim or rtrim can trigger CPU exhaustion with a string containing a long run of whitespace.

• https://github.com/scottchiefbaker/String-Util/commit/f8150867aaeb8f57c59601aefb2193f2caed8745.patch
• https://metacpan.org/release/BAKERSCOT/String-Util-1.36/diff/BAKERSCOT/String-Util-1.35#lib/String/Util.pm
• https://github.com/scottchiefbaker/String-Util/releases