CVE-2026-44195: OPNsense lockout_handler authentication lockout bypass

CVE-2026-44195 · Severity: medium · CVSS 5.3 · Published 2026-05-13

OPNsense is an open-source firewall and routing platform used to secure network traffic. A flaw in its login protection system allows attackers to bypass automatic lockouts by using specially crafted usernames that trick the system into thinking a login was successful. This allows an attacker to perform unlimited password-guessing attacks against the web interface or SSH service without being blocked, potentially leading to unauthorized access to the network's security infrastructure.

Technologies: OPNsense. Vendors: OPNsense.

Quick answers

Is CVE-2026-44195 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-44195 being exploited in the wild.
How severe is CVE-2026-44195?
Medium severity, with a CVSS score of 5.3, published 13 May 2026.
Which products and versions are affected?
OPNsense < 26.1.7.
Is there a fix for CVE-2026-44195?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-44195 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-44195?
Check whether you run OPNsense at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A logic flaw exists in the OPNsense 'lockout_handler' script, which processes syslog events to manage the 'sshlockout' firewall alias. The handler uses regular expressions to identify both failed and successful logins; however, it processes success patterns (like '.*Accepted.*') by explicitly resetting the failure counter for the source IP. Because the WebGUI logs include the raw username provided by the user, an unauthenticated attacker can submit a login attempt with a username such as 'Accepted'. The handler matches this against the success pattern and clears the attacker's failure count. By alternating between real password guesses and these crafted 'reset' attempts, an attacker can prevent their IP from ever reaching the lockout threshold, enabling indefinite brute-force attacks against the WebGUI and SSH. This is fixed in version 26.1.7 by prioritizing failure patterns over success patterns.

Affected products

  • OPNsense OPNsense core < 26.1.7

Timeline

  • 2026-04-30: advisory: Original GitHub security advisory published
  • 2026-05-13: disclosed: CVE published to NVD

References

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