# CVE-2026-110686: Cpanel::JSON::XS use-after-free in filter callbacks

Source: https://junglewise.ai/threats/cve-2026-110686-cpanel-json-xs-versions-before-4-80-for-perl-use-freed-filter  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-19. Updated: 2026-10-19  
License: CC BY 4.0 with a link back

CVE-2026-110686 · Severity: info · Published 2026-10-19

Cpanel::JSON::XS is a Perl library for parsing JSON data. When a custom filter callback removes itself during JSON decoding, the library may use freed memory to dispatch the next object, causing the process to crash. This affects any Perl application using this library with custom filters.

Technologies: [Cpanel::JSON::XS](https://junglewise.ai/threats/technologies/cpanel-json-xs). Vendors: [CPAN](https://junglewise.ai/threats/vendors/cpan).

## Quick answers

**Is CVE-2026-110686 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-110686 being exploited in the wild.

**How severe is CVE-2026-110686?** Informational severity, published 19 October 2026.

**Which products and versions are affected?** Cpanel::JSON::XS before 4.80.

**Is there a fix for CVE-2026-110686?** Yes: fixed in Cpanel::JSON::XS 4.80. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-110686 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-110686?** Check whether you run Cpanel::JSON::XS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Cpanel::JSON::XS 4.80

## Technical details

The vulnerability is a use-after-free in decode_hv where a filter callback that removes itself during decode causes the callback table to be freed while the decode operation is still in progress. Subsequent objects are dispatched through the freed memory without proper reference counting. The fix takes references to filter callbacks to keep them alive during the decode operation.

## Affected products

- CPAN Cpanel::JSON::XS before 4.80

## Timeline

- 2026-10-19: disclosed

## References

- [https://cpan.org/modules](https://cpan.org/modules)
- [https://github.com/rurban/Cpanel-JSON-XS/commit/c3e7e3c5b0b72d82b072c6a7cfb8c34cec4c7ea2.patch](https://github.com/rurban/Cpanel-JSON-XS/commit/c3e7e3c5b0b72d82b072c6a7cfb8c34cec4c7ea2.patch)

## Related threats

- [Cpanel::JSON::XS memory leak in encode_stringify](https://junglewise.ai/threats/cve-2026-110684-cpanel-json-xs-versions-from-3-0202-before-4-80-for-perl-leak)
- [Cpanel::JSON::XS use-after-free in ithread parser objects](https://junglewise.ai/threats/cve-2026-110681-cpanel-json-xs-versions-before-4-80-for-perl-use-the-parent)
- [Cpanel::JSON::XS out of bounds write in canonical hash encoding](https://junglewise.ai/threats/cve-2026-110680-cpanel-json-xs-versions-from-4-20-before-4-80-for-perl-write-out)
- [Cpanel::JSON::XS memory exhaustion in exponent encoding](https://junglewise.ai/threats/cve-2026-110676-cpanel-json-xs-versions-before-4-80-for-perl-allow-memory)