CVE-2026-39894: Cacti is an open source performance and fault management framework. In versions 1.2.30 and below, the locale-dependent decimal formatting in rrdtool_f...

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.

Metrics

CVSS 3.1

2.5/10

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS Probability

0.10%

1.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-474

Affected Software

Vendor	Product	Versions
Cacti	Cacti	< 1.2.31

References

https://github.com/Cacti/cacti/commit/d2a698854956e9e4e53da9eab5b5719ae40e6893Patch
https://github.com/Cacti/cacti/issues/7011Issue Tracking, Patch
https://github.com/Cacti/cacti/security/advisories/GHSA-23g4-vf2j-94w4Vendor Advisory

Timeline

Published: Jun 24, 2026
Last Modified: Jun 25, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-39894?

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.

How severe is CVE-2026-39894?

CVE-2026-39894 has a CVSS score of 2.5/10 (LOW severity). The EPSS model estimates a 0.10% probability of exploitation in the next 30 days.

How do I fix CVE-2026-39894?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.