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Kirby CVE-2020-26255

CRITICAL
Unrestricted Upload of File with Dangerous Type (CWE-434)
2020-12-08 security-advisories@github.com
9.1
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V5 - File Handling File type validation, storage isolation
MITRE ATT&CK

2 techniques across 2 tactics: Command and Control, Persistence

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 9.1 (CRITICAL). Attack characteristics: network attack vector, low complexity, high privileges required, no user interaction not required.

Exploit ScenarioDerived

A remote attacker could upload malicious files that can be executed on the server by sending crafted requests to the affected application.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 1.5% exploitation probability (EPSS)

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AnalysisAI

Kirby is a CMS. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, low attack complexity. This Unrestricted File Upload vulnerability could allow attackers to upload malicious files that can be executed on the server.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Validate file types server-side, store uploads outside webroot, use random filenames, scan for malware.

Affected Packages

composer getkirby/cms fix: 3.4.5
composer getkirby/panel fix: 2.5.14

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in composer

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Unrestricted File Upload (CWE-434), which allows attackers to upload malicious files that can be executed on the server. Kirby is a CMS. In Kirby CMS (getkirby/cms) before version 3.4.5, and Kirby Panel before version 2.5.14 , 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. 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. Affected products include: Getkirby Kirby, Getkirby Panel. Version information: version 3.4.5.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.1 CRITICAL
AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

DescriptionNVD

Kirby is a CMS. In Kirby CMS (getkirby/cms) before version 3.4.5, and Kirby Panel before version 2.5.14 , 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. 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.

Threat Intelligence Overview

EPSS Score
1.5%
Top 29% exploitable
Data Quality
3 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 1.5%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

47
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +46
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Malicious file upload attacks exploit insufficient validation when web applications accept user-provided files.

Affected Products (CPE)NVD

cpe:2.3:a:getkirby:kirby:*:*:*:*:*:*:*:*
cpe:2.3:a:getkirby:panel:*:*:*:*:*:*:*:*

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