CVE-2026-54003Network attack vector

Admin account creation via misclassified proxy headers

Published Jul 9, 2026 · Updated Jul 9, 2026

External initialization in Content Folder Kirby before 4.9.4 and 5.0.0 through 5.4.3 allows remote attackers to create the first admin user. Http\Environment::detectForwarded reads the Forwarded for value from parsed host parts, where that key never exists, while isLocal omits X-Client-IP and X-Real-IP. Exploitation requires a public, accountless site with Panel or API enabled behind a proxy that sets one of those headers, after which the attacker gains administrative access.

CVSS severity9.1
Critical
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

External initialization in Content Folder Kirby before 4.9.4 and 5.0.0 through 5.4.3 allows remote attackers to create the first admin user. Http\Environment::detectForwarded reads the Forwarded for value from parsed host parts, where that key never exists, while isLocal omits X-Client-IP and X-Real-IP. Exploitation requires a public, accountless site with Panel or API enabled behind a proxy that sets one of those headers, after which the attacker gains administrative access.

The record

CVE
CVE-2026-54003
Published
Jul 9, 2026
Updated
Jul 9, 2026
Vendor
Content Folder
Product
Kirby
Classifications
CWE-454, T1136
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.9.4
  2. Affected versionversion=>= 5.0.0, < 5.4.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Content Folder · Kirbyversion=< 4.9.4; version=>= 5.0.0, < 5.4.4

Published CVSS scores

9.1GitHubCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-454External Initialization of Trusted Variables or Data Stores
T1136Create Account

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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