# CVE-2026-110673: Cpanel::JSON::XS stack exhaustion in decode_tag with allow_tags

Source: https://junglewise.ai/threats/cve-2026-110673-cpanel-json-xs-versions-before-4-80-for-perl-allow-stack  
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-2026-110673 · Severity: info · Published 2026-10-19

Cpanel::JSON::XS is a JSON parsing library for Perl. When the allow_tags feature is enabled, an attacker can send specially crafted JSON with nested tagged values that bypass the max_depth limit and exhaust the C stack, causing the Perl process to crash with a segmentation fault. This can be exploited to deny service to applications that parse untrusted JSON.

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

## Quick answers

**Is CVE-2026-110673 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-110673 being exploited in the wild.

**How severe is CVE-2026-110673?** Informational severity, published 19 October 2026.

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

**Is there a fix for CVE-2026-110673?** Yes: fixed in Cpanel::JSON::XS 4.80. Until then: Disable the allow_tags feature if not required, or restrict parsing to trusted JSON sources until upgraded to version 4.80 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-110673 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-110673?** 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

Disable the allow_tags feature if not required, or restrict parsing to trusted JSON sources until upgraded to version 4.80 or later.

## Technical details

The vulnerability is a stack exhaustion flaw in the decode_tag function when allow_tags is enabled. Tagged values (marked by "(" syntax) are decoded recursively but were not counted against the max_depth limit, unlike arrays and objects. An attacker can send deeply nested tagged values (e.g., many "(" bytes in sequence) to exhaust the C stack and trigger an uncatchable segmentation fault. The fix charges tagged value decoding against max_depth to enforce the depth limit.

## Affected products

- 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/995eb484a9351753e2a8ec3317918b5b4a4e086a.patch](https://github.com/rurban/Cpanel-JSON-XS/commit/995eb484a9351753e2a8ec3317918b5b4a4e086a.patch)

## Related threats

- [Cpanel::JSON::XS canonical encoding misorders byte-string keys](https://junglewise.ai/threats/cve-2026-110687-cpanel-json-xs-versions-from-4-43-before-4-80-for-perl-misorder)
- [Cpanel::JSON::XS incremental parser number ambiguity in incr_parse](https://junglewise.ai/threats/cve-2026-110682-cpanel-json-xs-versions-from-4-42-before-4-80-for-perl-let-input)
- [Cpanel::JSON::XS memory leak in dupkeys_as_arrayref](https://junglewise.ai/threats/cve-2026-110677-cpanel-json-xs-versions-from-4-28-before-4-80-for-perl-leak-the)
- [Cpanel::JSON::XS type confusion in duplicate key handling](https://junglewise.ai/threats/cve-2026-110674-cpanel-json-xs-versions-from-4-33-before-4-80-for-perl-miss)
- [Cpanel::JSON::XS memory leak in decode_hv with rejected keys](https://junglewise.ai/threats/cve-2026-110672-cpanel-json-xs-versions-before-4-80-for-perl-leak-the-decoded)