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.
Weakness
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Libstring-util-perl | Ubuntu | questing | * |
| Libstring-util-perl | Ubuntu | upstream | * |
Potential Mitigations
Related Attack Patterns
References
- https://github.com/scottchiefbaker/String-Util/commit/f8150867aaeb8f57c59601aefb2193f2caed8745.patch
- https://github.com/scottchiefbaker/String-Util/releases
- https://metacpan.org/release/BAKERSCOT/String-Util-1.36/diff/BAKERSCOT/String-Util-1.35#lib/String/Util.pm
- http://www.openwall.com/lists/oss-security/2026/07/07/18