---
title: "CVE-2026-54003: Kirby: External Initialization of the Panel on reverse proxy setups with the `Forwarded` header"
url: https://erroneo.us/security/cve/CVE-2026-54003/
description: "CVE-2026-54003 (getkirby/cms (Composer (PHP))): Kirby is an open-source content management system. Prior to 4.9.4 and from 5.4.4, Kirby sites with no…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-09
date_modified: 2026-07-09
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-54003"
kev: false
cvss: 9.1
epss: 0.00743
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-54003: Kirby: External Initialization of the Panel on reverse proxy setups with the `Forwarded` header

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.7% , percentile 54: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 54% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes getkirby/cms (Composer (PHP)) <= 4.9.3, fixed in 4.9.4 ; getkirby/cms (Composer (PHP)) >= 5.0.0-alpha.1, <= 5.4.3, fixed in 5.4.4 . Check your lockfile, including transitive dependencies.

## What it is

Kirby is an open-source content management system. Prior to 4.9.4 and from 5.4.4, Kirby sites with no configured user accounts that run on publicly accessible servers behind a reverse proxy setting the Forwarded, X-Client-IP, or X-Real-IP request header could allow remote attackers to install the Panel and create the first admin user because local-IP checks trusted those headers incorrectly. This issue is fixed in versions 4.9.4 and 5.4.4.

## Affected packages

- Composer (PHP) `getkirby/cms` <= 4.9.3 → fixed: 4.9.4
- Composer (PHP) `getkirby/cms` >= 5.0.0-alpha.1, <= 5.4.3 → fixed: 5.4.4

## Affected products (CVE record)

- getkirby kirby: < 4.9.4, >= 5.0.0, < 5.4.4

## Severity

- GitHub_M CVSS 4.0: 9.1 `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`
- GitHub CVSS 4.0: 9.1 `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 0.74% probability of exploitation activity in the next 30 days; percentile 54.

## Sources

- [GitHub Advisory GHSA-whxw-24jc-cwmv](https://github.com/advisories/GHSA-whxw-24jc-cwmv)
- [CVE.org record CVE-2026-54003](https://www.cve.org/CVERecord?id=CVE-2026-54003)
- [NVD entry CVE-2026-54003](https://nvd.nist.gov/vuln/detail/CVE-2026-54003)
- [github.com](https://github.com/getkirby/kirby/security/advisories/GHSA-whxw-24jc-cwmv)
- [github.com](https://github.com/getkirby/kirby/pull/8166)
- [github.com](https://github.com/getkirby/kirby/commit/1c7fee90e49153cf9ca4a6ec17481d25fbedc48d)
- [github.com](https://github.com/getkirby/kirby/commit/3423f66c01dbc0455862e23ee699d2aa469f3234)
- [github.com](https://github.com/getkirby/kirby/commit/66a3a14bf0892d320723ba766cd5f1d33a51d15b)
- [github.com](https://github.com/getkirby/kirby/commit/ab992dc149610b90e337c2955ab6ccb7f72ffb3a)
- [github.com](https://github.com/getkirby/kirby/releases/tag/4.9.4)
- [github.com](https://github.com/getkirby/kirby/releases/tag/5.4.4)

---
Source page: https://erroneo.us/security/cve/CVE-2026-54003/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt