How severe is CVE-2020-26255?

CVE-2020-26255 has a CVSS score of 9.1/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-26255?

CVE-2020-26255 affects the following packages: getkirby/panel (Packagist), getkirby/cms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2020-26255?

Update getkirby/panel to 2.5.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-26255 is resolved across your whole dependency graph.

How do I detect CVE-2020-26255 in my Packagist dependencies?

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

How do I mitigate CVE-2020-26255 if there is no patch (or I can't update yet)?

Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

Is CVE-2020-26255 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-26255 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-2020-26255?

CVE-2020-26255 has an EPSS (Exploit Prediction Scoring System) score of 1.5%, placing it in the 73th 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-2020-26255?

CVE-2020-26255 is classified as Unrestricted File Upload (CWE-434). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-26255 published, and has it been updated?

CVE-2020-26255 was published on December 8, 2020 and was last updated on August 27, 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

CRITICAL severity

CVE-2020-26255 — panel

CRITICALFix: getkirby-v2/panel@5a569d4

CVE-2020-26255 is a critical-severity (CVSS 9.1) Unrestricted File Upload vulnerability in getkirby/panel. A fix is available for getkirby/panel — see the affected versions and patch details below.

Kirby Panel users could upload PHP Phar archives as content files before v2.5.14 and v3.4.5

Also known asGHSA-g3h8-cg9x-47qw

Published

Dec 8, 2020

Updated

Aug 27, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs73th percentile — riskier than 73% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-26255 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

🐘getkirby/panel🐘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

Impact

An editor with full access to the Kirby Panel can upload a PHP .phar file and execute it on the server. This vulnerability is critical if you might have potential attackers in your group of authenticated Panel users, as they can gain access to the server with such a Phar file.

Visitors without Panel access cannot use this attack vector.

Patches

The problem has been patched in Kirby 2.5.14 and Kirby 3.4.5. Please update to one of these or a later version to fix the vulnerability.

Note: Kirby 2 reaches end of life on December 31, 2020. We therefore recommend to upgrade your Kirby 2 sites to Kirby 3. If you cannot upgrade, we still recommend to update to Kirby 2.5.14.

Workarounds

Kirby 2 sites on older releases can also be patched by applying the changes from this commit.

Credits

Thanks to Thore Imhof of Accenture for reporting the problem.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`getkirby/panel`	all versions	2.5.14`composer require getkirby/panel:^2.5.14`
🐘Packagist	`getkirby/cms`	≥ 3.0.0&&< 3.4.5	3.4.5`composer require getkirby/cms:^3.4.5`

Affected Products

2 products · 2 configurations

Application

kirbygetkirby

< 3.4.5

range

Application

panelgetkirby

< 2.5.14

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for getkirby/panel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update getkirby/panel to 2.5.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-26255 is resolved across your whole dependency graph.
Workarounds
Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

Frequently Asked Questions

### Impact An editor with full access to the Kirby Panel can upload a PHP `.phar` file and execute it on the server. This vulnerability is critical if you might have potential attackers in your group of authenticated Panel users, as they can gain access to the server with such a Phar file. Visitors without Panel access *cannot* use this attack vector. ### Patches The problem has been patched in [Kirby 2.5.14](https://github.com/getkirby-v2/panel/releases/tag/2.5.14) and [Kirby 3.4.5](https://github.com/getkirby/kirby/releases/tag/3.4.5). Please update to one of these or a [later version](h