How severe is CVE-2026-42051?

No CVSS score has been assigned to CVE-2026-42051 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42051?

CVE-2026-42051 affects the following packages: getkirby/cms (Packagist), getkirby/cms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-42051?

Update getkirby/cms to 4.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42051 is resolved across your whole dependency graph.

How do I detect CVE-2026-42051 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for getkirby/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42051 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-42051?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42051 can be triaged on real exposure rather than presence alone.

Is CVE-2026-42051 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42051 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42051?

CVE-2026-42051 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 9th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42051?

CVE-2026-42051 is classified as CWE-862 (CWE-862). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42051 published, and has it been updated?

CVE-2026-42051 was published on May 9, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2026-42051 — getkirby/cms

CVE-2026-42051 is a CWE-862 vulnerability in getkirby/cms. A fix is available for getkirby/cms — see the affected versions and patch details below.

Kirby: System API endpoint leaks license data and installed version to authenticated users

Also known asGHSA-x68m-c7jf-2572

Published

May 9, 2026

Updated

Aug 12, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Sep 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42051.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs9th percentile — riskier than 9% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

2 pkgs affected

🐘getkirby/cms🐘getkirby/cms

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

TL;DR

This vulnerability affects all Kirby sites that might have potential attackers in the group of authenticated Panel users.

Introduction

Missing authorization allows authenticated users to perform actions they are not intended to have access to.

The effects of missing authorization can include unauthorized access to sensitive information as well as unauthorized changes to content or system information.

Impact

Kirby's user permissions control which user role is allowed to perform specific actions in the CMS. These permissions are defined for each role in the user blueprint (site/blueprints/users/...). The permissions control the authorization of user actions (with handling of model-specific authorization omitted here for brevity).

Kirby provides the access.system permission (among others) that controls access to the system area of the Kirby Panel. This area contains internal system information like the installed Kirby, plugin and server versions, security state and Kirby license. If the access.system permission is disabled for a user role, users of that role should not be able to access this internal system information. However it is also possible to access some system information via the /api/system REST API endpoint. In affected releases, the response of this endpoint for authenticated users contained the installed Kirby version and the status, type and code of the installed Kirby license. These values are considered sensitive information and should be protected by the access.system permission.

The installed Kirby version and license data can be used by malicious actors during reconnaissance when planning a separate attack.

Patches

The problem has been patched in Kirby 4.9.0 and Kirby 5.4.0. Please update to one of these or a later version to fix the vulnerability.

In all of the mentioned releases, we have protected the version and license properties of the /api/system endpoint with a check for the existing access.system permission. This ensures that the REST API only outputs information that should be accessible to the user via the Panel.

Credits

Kirby thanks @HuajiHD and @0x-bala for responsibly reporting the identified issue.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`getkirby/cms`	all versions	4.9.0`composer require getkirby/cms:^4.9.0`
🐘Packagist	`getkirby/cms`	≥ 5.0.0&&< 5.4.0	5.4.0`composer require getkirby/cms:^5.4.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for getkirby/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update getkirby/cms to 4.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42051 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42051 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-42051. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### TL;DR This vulnerability affects all Kirby sites that might have potential attackers in the group of authenticated Panel users. ---- ### Introduction Missing authorization allows authenticated users to perform actions they are not intended to have access to. The effects of missing authorization can include unauthorized access to sensitive information as well as unauthorized changes to content or system information. ### Impact Kirby's user permissions control which user role is allowed to perform specific actions in the CMS. These permissions are defined for each role in the user blu

O3 Security · Impact-Aware SCA

Is CVE-2026-42051 in your dependencies?

O3 Security finds CVE-2026-42051 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works