CVE-2026-21861 baserCMS: OS Command Injection Leading to Remote Code Execution (RCE)

Critical 9.1 Published 31 Mar 2026 Updated 31 Mar 2026

An authenticated administrator can execute arbitrary OS commands on the server via the core update functionality in baserCMS.

Exploited in the wild: Not known
Login needed: An administrator
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-21861?

CVE-2026-21861 is a critical command injection vulnerability in Basercms Basercms, published on 31 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.

Official description

baserCMS is a website development framework. Prior to version 5.2.3, baserCMS contains an OS command injection vulnerability in the core update functionality. An authenticated administrator can execute arbitrary OS commands on the server due to improper handling of user-controlled input that is directly passed to exec() without sufficient validation or escaping. This issue has been patched in version 5.2.3.

Weakness: CWE-78

Which versions are affected by CVE-2026-21861?

2 open source packages ship an affected version, including baserproject/basercms. It affects 1 product.

Package	Affected	Fixed in
`baserproject/basercms` Packagist	All versions	`5.2.3`
`baserproject/basercms` Packagist	All versions	`5.2.3`

Products include Basercms Basercms.

How do I fix CVE-2026-21861?

Upgrade baserproject/basercms to 5.2.3 or later.

Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.

Is CVE-2026-21861 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-21861 exists.

All Basercms Basercms vulnerabilities

Sources

Also known as GHSA-qxmc-6f24-g86g.