CVE-2026-63442 opnsense CVE debrief

Who should care

Administrators of OPNsense systems, security teams, and IT personnel responsible for system maintenance and security. They should verify their version and apply the patch if necessary. The vulnerability allows for log forgery via the login username field in the WebGUI authentication, which can lead to IP blocking and bypassing of password-guessing lockout.

Why it matters

The CVE-2026-63442 vulnerability in OPNsense allows for log forgery via the login username field in the WebGUI authentication. This can lead to IP blocking and bypassing of password-guessing lockout. Administrators of OPNsense systems should verify their version and apply the patch if necessary. The issue is fixed in version 26.1.11.

• Potential IP blocking of administrative, DNS, gateway, or monitoring addresses
• Bypassing of password-guessing lockout without authentication
• Forged failure events for another IP, causing that IP to be added to the sshlockout PF table and its active states to be killed
• Forged accepted events that reset an attacker's own brute-force counter

Technical summary

The OPNsense system is vulnerable to log forgery via the login username field in the WebGUI authentication. This can lead to IP blocking and bypassing of password-guessing lockout. An attacker with network access to the login page can forge failure events for another IP, causing that IP to be added to the sshlockout PF table and its active states to be killed. The issue is fixed in version 26.1.11. Administrators should verify their version and apply the patch if necessary. The vulnerability allows for log forgery via the login username field in the WebGUI authentication.

Defensive priority

Administrators of OPNsense systems should verify their version and apply the patch if necessary.

Recommended defensive actions

• Verify OPNsense version and apply patch if necessary
• Review system logs for potential log forgery attempts
• Monitor system for unusual activity
• 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
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details on the log forgery vulnerability in OPNsense. The issue is fixed in version 26.1.11. Administrators of OPNsense systems should verify their version and apply the patch if necessary. The vulnerability allows for log forgery via the login username field in the WebGUI authentication, which can lead to IP blocking and bypassing of password-guessing lockout.

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.