---
id: "CVE-2026-110674"
kind: "vulnerability"
aliases: ["CVE-2026-110674"]
title: "Cpanel::JSON::XS: duplicate bare keys can crash Perl or read chosen memory"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["cpan", "cpanel-json-xs", "json-parsing", "package", "perl"]
not_affected_if: ["default-config", "trusted-input-only"]
published_at: "2026-10-19T19:17:21+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-2026-110674", "first_seen_at": "2026-10-23T21:57:18+00:00"}]
---

# Cpanel::JSON::XS: duplicate bare keys can crash Perl or read chosen memory

Cpanel::JSON::XS versions 4.33 to before 4.80 mishandle duplicate non-ASCII bare keys when decoding with relaxed and dupkeys_as_arrayref, so a repeated key can replace an array with a plain value. The next repeat then treats a JSON integer as a pointer, letting untrusted JSON crash the process or dereference an address chosen by a number.

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

## How to check

- Run `perl -MCpanel::JSON::XS -e 'print $Cpanel::JSON::XS::VERSION'` to read the installed version.
- Search the codebase for `dupkeys_as_arrayref` and `allow_barekey` or `relaxed` in JSON decoder setup.
- Check whether untrusted input reaches the decoder with those options enabled.

## Fix

- Upgrade Cpanel::JSON::XS to `4.80` or later.
- Until upgraded, stop decoding untrusted JSON with `relaxed` together with `dupkeys_as_arrayref`.

## Timeline

- 2026-10-23T21:57:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-110674

## From the sources

Cpanel::JSON::XS versions from 4.33 before 4.80 for Perl miss duplicate non-ASCII bare keys, allowing type confusion under dupkeys_as_arrayref in decode_hv.

With allow_barekey, which relaxed enables, a bare key containing a non-ASCII byte is stored as UTF-8 but looked up as raw bytes, so a repeated key escapes the duplicate-key check and replaces the earlier value.

From 4.41, under dupkeys_as_arrayref, a bare repeat replaces the array that collects a key's values with a plain value, and the next quoted repeat pushes onto that value as if it were an array. A JSON integer there is dereferenced as a pointer.

Untrusted JSON decoded with relaxed and dupkeys_as_arrayref can crash the process or dereference an address chosen by a JSON number.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_