---
id: "CVE-2026-57154"
kind: "vulnerability"
aliases: ["CVE-2026-57154"]
title: "OPNsense: line injection in settings lets delegated users alter privileged configs"
severity: "high"
cvss: 8.1
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["dnsmasq", "firewall", "freebsd", "monit", "opnsense", "other"]
not_affected_if: ["fixed-version", "no-delegated-users"]
published_at: "2026-11-03T19:18:06+00:00"
first_seen_at: "2026-11-03T19:44:53+00:00"
updated_at: "2026-11-03T19:45:29+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-57154", "first_seen_at": "2026-11-03T19:44:53+00:00"}]
---

# OPNsense: line injection in settings lets delegated users alter privileged configs

Authenticated Web UI or API users with delegated access can submit carriage return or line feed characters in single-line fields, which get written into privileged service configuration files. An attacker can add directives that change service behavior beyond their delegated scope, and the Monit path was shown to allow root command execution.

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

## How to check

- Check the installed OPNsense version in the Web UI dashboard or with `opnsense-version`, and compare it with the fixed versions.
- Review which users hold delegated access to services such as Dnsmasq, Monit, OpenVPN or the firewall settings.

## Fix

- OPNsense: move to `26.1.11` or `26.4.1p1`, the versions the sources state fix the issue.

## Timeline

- 2026-11-03T19:44:53+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-57154

## Documents

- [advisory] Vendor advisory: github.com https://github.com/opnsense/core/security/advisories/GHSA-fq94-cxvc-9r7w
- [fix] Patch: github.com https://github.com/opnsense/core/commit/52b18e67a9ec4596a64ac3a53f3aa102ced55293
- [fix] Patch: github.com https://github.com/opnsense/core/commit/6c3be9a11699879fe50aea1c30e50de5864601d7

## From the sources

OPNsense is a FreeBSD based firewall and routing platform. Prior to 26.1.11 and 26.4.1p1, authenticated Web UI or API users with delegated access to affected settings can submit CR or LF characters in fields expected to contain one line, causing generated privileged service configuration files to contain additional attacker-controlled directives or policy lines. The confirmed Dnsmasq path includes dhcp_boot.filename, dhcp_boot.servername, dhcp_boot.address, and dhcp_options.value, which are rendered into /usr/local/etc/dnsmasq.conf; access through page-services-dnsforwarder covers api/dnsmasq/*. Related affected fields span OpenVPN, DHCPv6, Unbound, IPsec, NTP, PPP or MPD, Monit, firewall, sudo, WebGUI, and System General configuration. Applying or restarting the affected service can alter behavior beyond the delegated setting, create service-side files, cross RBAC boundaries, or cause denial of service. Line injection through Monit mail password and adjacent Monit text fields into /usr/local/etc/monitrc demonstrated root command execution. Arbitrary shell command execution was not confirmed for the Dnsmasq path. This issue is fixed in versions 26.1.11 and 26.4.1p1.

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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_