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OpnsenseApplication

CVE-2026-45158

CRITICAL · 9.1 CVSS v3.1 Published 2026-05-13
Fix available
A fix is available. Upgrade to 26.1.8 or later.
See remediation →
97/100
Remediation priority · Urgent
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
OPNsense is a FreeBSD based firewall and routing platform. Prior to 26.1.8, unsanitized user input is passed to the DHCP configuration of the configured interface, which is processed by a shell script, allowing remote code execution as root on the underlying operating system. This vulnerability is fixed in 26.1.8.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

OPNsense versions prior to 26.1.8 contain a remote code execution vulnerability where unsanitized user input in the DHCP configuration for a configured interface is passed to a shell script without proper sanitization, allowing authenticated remote attackers to execute arbitrary commands as root on the underlying FreeBSD operating system.

MitigationUpgrade OPNsense to version 26.1.8 or later to patch the vulnerability. If immediate upgrading is not possible, restrict access to the DHCP configuration interface to trusted users only.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
OpnsenseApplication
Affected:< 26.1.8

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check OPNsense version
    Log into the OPNsense web UI and navigate to System > Dashboard, or run 'opnsense-version' via SSH to retrieve the installed version number.
    Affected if The installed version is less than 26.1.8
  2. Verify DHCP service is configured
    In the OPNsense web UI, navigate to Services > DHCPv4 and/or DHCPv6. Check whether DHCP is enabled on any interface (the LAN interface or other interfaces).
    Affected if DHCP server is enabled and configured on one or more interfaces using OPNsense versions prior to 26.1.8
  3. Identify configured DHCP ranges and options
    In Services > DHCPv4 (or DHCPv6), review the DHCP range settings, static mappings, and any custom options defined. These are the fields where unsanitized input could be passed to shell scripts.
    Affected if Any DHCP configuration fields are populated on an affected OPNsense version (prior to 26.1.8)

A user is affected if their OPNsense installation is version 26.1.8 or earlier and has DHCP server enabled on any interface, as this configuration path contains the vulnerable code accepting unsanitized input.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 26.1.8 or later
Fixed in 26.1.8
Interim mitigation

Upgrade OPNsense to version 26.1.8 or later to patch the vulnerability. If immediate upgrading is not possible, restrict access to the DHCP configuration interface to trusted users only.

Recommended fix High confidence

OPNsense 26.1.8

  1. 1. Backup the current OPNsense configuration before performing any upgrade.
  2. 2. Verify current OPNsense version is below 26.1.8 using the web interface (System: Firmware: Status) or command line: opnsense-version
  3. 3. Navigate to System: Firmware: Settings and configure update mirrors if needed.
  4. 4. Go to System: Firmware: Status and click 'Check for updates' to fetch available updates.
  5. 5. If update to 26.1.8 is available, proceed with the firmware upgrade following standard OPNsense upgrade procedure.
  6. 6. After upgrade completes, verify the system is running version 26.1.8 or later.
  7. 7. Review DHCP interface configuration to ensure existing settings are intact and functioning correctly.
Caveat Point release upgrade within same branch; minimal risk but always backup config before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Opnsense Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.

Scan for this in your stack

Free · runs locally
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-45158 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data