GHSA-qv4q-mr5r-qprj

## Summary

Nokogiri `1.13.8, 1.13.9` fails to check the return value from `xmlTextReaderExpand` in the method `Nokogiri::XML::Reader#attribute_hash`. This can lead to a null pointer exception when invalid markup is being parsed.

For applications using `XML::Reader` to parse untrusted inputs, this may potentially be a vector for a denial of service attack.

## Mitigation

Upgrade to Nokogiri `>= 1.13.10`.

Users may be able to search their code for calls to either `XML::Reader#attributes` or `XML::Reader#attribute_hash` to determine if they are affected.

## Severity

The Nokogiri maintainers have evaluated this as [High Severity 7.5 (CVSS3.1)](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

## References

- [CWE - CWE-252: Unchecked Return Value (4.9)](https://cwe.mitre.org/data/definitions/252.html) - [CWE - CWE-476: NULL Pointer Dereference (4.9)](https://cwe.mitre.org/data/definitions/476.html)

## Credit

This vulnerability was responsibly reported by @davidwilemski.