What is CVE-2026-21861?

CVE-2026-21861 is a critical-severity vulnerability in Basercms, classified under OS Command Injection. CVSS score: 9.1/10. Published 2026-03-31.

How severe is CVE-2026-21861?

Critical severity. CVSS v3 base score is 9.1 out of 10.

RCE in Basercms

CVE-2026-21861

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.

Vulnerability class: Command Injection (OS Command Injection)

EPSS: 0.023 (81.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H.

Affected products

Basercms
Baserproject Basercms — versions < 5.2.3

Weakness classification (CWE)

CWE-78 — OS Command Injection

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
security-advisories@github.com (x_refsource_MISC, Vendor Advisory)
security-advisories@github.com (x_refsource_MISC, Release Notes)

Frequently asked questions

What is CVE-2026-21861?: CVE-2026-21861 is a critical-severity vulnerability in Basercms, classified under OS Command Injection. CVSS score: 9.1/10. Published 2026-03-31.
How severe is CVE-2026-21861?: Critical severity. CVSS v3 base score is 9.1 out of 10.