---
id: "CVE-2026-110677"
kind: "vulnerability"
aliases: ["CVE-2026-110677"]
title: "Cpanel::JSON::XS: duplicate-key decoding leaks memory, exhausting process memory"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["cpanel-json-xs", "package", "perl", "self-hosted"]
not_affected_if: ["default-config", "trusted-input"]
published_at: "2026-10-19T19:17:21+00:00"
first_seen_at: "2026-10-23T21:57:18+00:00"
updated_at: "2026-10-25T05:10:49+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-110677", "first_seen_at": "2026-10-23T21:57:18+00:00"}]
---

# Cpanel::JSON::XS: duplicate-key decoding leaks memory, exhausting process memory

Cpanel::JSON::XS versions 4.28 before 4.80 for Perl leak the array that collects duplicate key values when dupkeys_as_arrayref is used. Repeatedly decoding untrusted JSON with a duplicate key holding a large value can exhaust process memory, causing a denial of service.

_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'` and see whether the version is between `4.28` and `4.79`
- Search the codebase for `dupkeys_as_arrayref` to find code that uses the affected option

## Fix

- Upgrade Cpanel::JSON::XS to `4.80` or later
- Until upgraded, avoid `dupkeys_as_arrayref` when decoding untrusted input

## Timeline

- 2026-10-23T21:57:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-110677

## From the sources

Cpanel::JSON::XS versions from 4.28 before 4.80 for Perl leak the array collecting duplicate key values under dupkeys_as_arrayref in decode_hv.

With dupkeys_as_arrayref, the values of a duplicate object key are collected into a new array. An extra reference is never released, so the array and every value in it outlive the decoded structure. The array also leaks when decoding fails after a duplicate key.

Repeatedly decoding untrusted JSON with a duplicate key holding a large value exhausts process memory.

---

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