Nokogiri XSLT transform has a memory leak

Summary

Nokogiri's Nokogiri::XSLT::Stylesheet#transform leaks a small heap allocation when passed a Ruby string parameter containing a null byte.

For applications that pass attacker-controlled input through XSLT.transform parameters, this may be a vector for a denial of service attack against long-running processes.

Mitigation

Upgrade to Nokogiri >= 1.19.3.

Users may also be able to mitigate this issue without upgrading by validating untrusted transform parameters before passing them to Nokogiri::XSLT::Stylesheet#transform.

Severity

The Nokogiri maintainers have evaluated this as Moderate Severity, CVSS 5.3.

Each leaked allocation is approximately 24–32 bytes, so meaningful memory growth requires sustained attacker-controlled traffic at high call rates. The bug does not cause memory corruption, information disclosure, or any change in the behavior of the transform itself, and the string-handling exception is raised as expected.

Applications that do not pass raw attacker-controlled bytes to XSLT parameters are unlikely to be affected in practice.

Resources

• CWE-401: Missing Release of Memory after Effective Lifetime

Credit

This vulnerability was responsibly reported by @Captainjack-kor.