---
id: "CVE-2026-39902"
kind: "vulnerability"
aliases: ["CVE-2026-39902"]
title: "Cacti: weak input blocklist lets admins run shell commands"
severity: "high"
cvss: 7.2
epss: 0.00572
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["cacti", "package", "php", "self-hosted"]
not_affected_if: ["auth-required", "patched-version"]
published_at: "2026-10-23T15:17:30+00:00"
first_seen_at: "2026-10-23T21:57:34+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-39902", "first_seen_at": "2026-10-23T21:57:34+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-39902", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Cacti: weak input blocklist lets admins run shell commands

Cacti, an open source network monitoring framework, filters input with a blocklist that misses quotes, redirects and subshell characters. An authenticated admin can save a crafted input string that gets past the filter and runs shell commands on the server.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `php -r 'echo CACTI_VERSION;'` or check the version shown in the Cacti web footer and confirm it is below `1.2.31`
- Check the Cacti install for the input_string handling in the data input configuration if the version is unclear

## Fix

- Upgrade Cacti to `1.2.31` or later
- Until upgraded, limit admin accounts to trusted staff

## Timeline

- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-39902
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-39902

## From the sources

Cacti is an open source performance and fault management framework. Prior to version 1.2.31, the prior blocklist ([;&| `$\\n\r]) omitted single-quote, double-quote, redirect operators, subshell parens and braces. An authenticated admin could save an input_string` containing single-quote, redirect operator, or subshell parens, and pass the check. This issue has been patched in version 1.2.31.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_