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Remote code execution (RCE) from PHP Phar archives uploaded by Panel users as content files

Critical
bastianallgeier published GHSA-g3h8-cg9x-47qw Dec 2, 2020

Package

composer getkirby/panel, getkirby/cms (Composer)

Affected versions

<=2.5.13, 3.0.0-3.4.4

Patched versions

2.5.14, 3.4.5

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.

Severity

Critical
10.0
/ 10

CVSS base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVE ID

CVE-2020-26255

Weaknesses