CVE-2026-57155 opnsense CVE debrief

Who should care

OPNsense administrators and users, security teams responsible for monitoring and patching vulnerabilities, and individuals with access to OPNsense systems should be aware of this vulnerability and take necessary actions to mitigate it.

Why it matters

This critical vulnerability in OPNsense requires immediate attention from administrators and security teams to prevent potential exploitation and compromise of firewall systems.

• Potential for complete firewall compromise
• Arbitrary file write as root via GeoIP Alias Importer
• Execution of commands as root through crafted newsyslog fragment and oversized log file
• Possible lateral movement and further exploitation within the network

Technical summary

The OPNsense GeoIP Alias Importer is vulnerable to arbitrary file write, allowing an attacker with Firewall Alias Edit privilege to write content as root. This can lead to complete firewall compromise through a crafted newsyslog fragment and oversized log file. The issue is fixed in version 26.1.11. An attacker-controlled GeoIP source URL can be supplied, and an archive with a malicious country code can be used to write arbitrary content as root with an -IPv4 or -IPv6 suffix. A user with Firewall Alias Edit privilege can configure the attacker-controlled GeoIP source URL.

Defensive priority

High priority for OPNsense administrators to update to version 26.1.11 or later, verify and restrict access to GeoIP Alias Importer functionality, and closely monitor system logs for suspicious activity.

Recommended defensive actions

• Update OPNsense to version 26.1.11 or later
• Verify and restrict access to GeoIP Alias Importer functionality
• Closely monitor system logs for suspicious activity
• Implement additional security measures to detect and prevent potential attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The CVE record and source item provide details on the vulnerability, its impact, and the affected versions. However, there is limited information on potential exploits or attacks in the wild. OPNsense administrators should verify and restrict access to GeoIP Alias Importer functionality and closely monitor system logs for suspicious activity. The issue is fixed in version 26.1.11. There are no known reports of exploitation in the wild, but given the critical severity, defenders should treat this as a high-priority update.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.