CVE-2026-39894

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.

CVSS v3.1 Score

2.9

LOW

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

EPSS — Exploit Prediction

0.0010

Probability of exploitation

0.01%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-474 CWE-474

Affected Products

Vendor	Product	Versions
cacti	cacti	< 1.2.31

References

Advisories & Patches

https://github.com/Cacti/cacti/commit/d2a698854956e9e4e53da9eab5b5719ae40e6893 https://github.com/Cacti/cacti/issues/7011 https://github.com/Cacti/cacti/security/advisories/GHSA-23g4-vf2j-94w4

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. It has a CVSS v3.1 base score of 2.9 (LOW).

How severe is CVE-2026-39894? +

CVE-2026-39894 has a CVSS v3.1 score of 2.9 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0010, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-39894? +

CVE-2026-39894 affects products from cacti, specifically: cacti. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-39894? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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