CVE-2026-39894 Cacti: RRDtool metric shift via LC_NUMERIC locale comma decimal formatting

Low 2.9 Published 24 Jun 2026 Updated 25 Jun 2026

Cacti corrupts RRDtool metrics if the server locale uses comma decimal separators, requiring a locale misconfiguration to trigger data integrity issues.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-39894?

CVE-2026-39894 is a low-severity vulnerability in Cacti Cacti, published on 24 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

Cacti is an open source performance and fault management framework. In versions 1.2.30 and below, the locale-dependent decimal formatting in rrdtool_function_update() can corrupt RRDtool metric values. The rrdtool_function_update() function checks metric values with is_numeric() and concatenates them into the RRDtool update command via PHP string interpolation. PHP's string cast of floats is locale-sensitive: if LC_NUMERIC uses comma as decimal separator (e.g., de_DE), a value of 1.5 becomes "1,5". RRDtool expects . as decimal separator, causing metric data to shift into wrong columns or be silently dropped. No setlocale() reset is present in the update path. This causes a data integrity issue, but is not remotely exploitable; it requires server locale misconfiguration. The issue has been fixed in version 1.2.31.

Weakness: CWE-474

Which versions are affected by CVE-2026-39894?

It affects 1 product.

Products include Cacti Cacti.

How do I fix CVE-2026-39894?

Upgrade to a fixed version.

Is CVE-2026-39894 being exploited?

There is no known exploitation of CVE-2026-39894 in the wild and no public exploit code.

All Cacti Cacti vulnerabilities

Sources

Also known as DEBIAN-CVE-2026-39894, GHSA-23g4-vf2j-94w4, UBUNTU-CVE-2026-39894.