---
id: "CVE-2026-110673"
kind: "vulnerability"
aliases: ["CVE-2026-110673"]
title: "Cpanel::JSON::XS: nested tagged values crash Perl process via stack exhaustion"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["cpanel-json-xs", "json-parsing", "package", "perl"]
not_affected_if: ["allow-tags-disabled", "trusted-input-only"]
published_at: "2026-10-19T19:17:20+00:00"
first_seen_at: "2026-10-23T21:57:18+00:00"
updated_at: "2026-10-25T05:10:54+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-110673", "first_seen_at": "2026-10-23T21:57:18+00:00"}]
---

# Cpanel::JSON::XS: nested tagged values crash Perl process via stack exhaustion

Cpanel::JSON::XS before 4.80 decodes nested tagged values under allow_tags recursively without counting them against max_depth. A crafted input of repeated "(" bytes exhausts the C stack and causes an uncatchable segmentation fault, crashing the process.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed version with `perl -MCpanel::JSON::XS -e 'print $Cpanel::JSON::XS::VERSION'`
- Search dependencies for `allow_tags` usage, e.g. `grep -rn allow_tags` in the codebase
- unknown whether other check methods exist beyond this

## Fix

- Upgrade Cpanel::JSON::XS to `4.80` or later
- Until upgraded, avoid decoding untrusted input with `allow_tags` enabled

## Timeline

- 2026-10-23T21:57:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-110673

## From the sources

Cpanel::JSON::XS versions before 4.80 for Perl allow stack exhaustion via nested tagged values under allow_tags in decode_tag.

With allow_tags, "(" starts a tagged value. Its tag and value are decoded recursively, and each can start another tagged value. Unlike arrays and objects, this nesting is not counted against max_depth.

A run of "(" bytes exhausts the C stack and triggers an uncatchable segmentation fault regardless of max_depth.

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