Loading vulnerability…
Authentication Bypass via Path Traversal in UniFi OS
CVE-2026-54403 is a path traversal vulnerability affecting certain UniFi OS devices and instances. The flaw allows a remote attacker on the network to leverage path traversal behavior to bypass authentication controls on affected UniFi OS deployments. Available reporting characterizes the issue as exploitable by a low-privileged attacker, while also noting that it may be chainable with other vulnerabilities to remove or bypass that low-privilege requirement entirely in some attack paths. Affected versions include UniFi OS / Server 5.1.15 and earlier, UniFi OS 5.1.18 and earlier as referenced in advisory summaries, UniFi Network Attached Storage 5.1.16 and earlier for impacted subsets, and EF-Core 5.1.18 and earlier where UniFi OS vulnerabilities apply.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation enables authentication bypass on affected UniFi OS devices or instances. This can allow an attacker to access functionality that should be restricted to authenticated users and may serve as an entry point for further compromise. Reporting also indicates the vulnerability can be combined with other flaws, increasing the likelihood of privilege escalation, unauthorized system or configuration changes, and broader compromise of the affected device.
If you can’t patch tonight, do this now.
No interim workaround information is available. The primary mitigation is prompt installation of the vendor-provided patched versions. Until updates can be applied, reduce exposure by limiting network access to management interfaces and restricting access to trusted administrative networks only, recognizing that such measures are compensating controls rather than a fix.
Patch, then assume compromise.
Upgrade affected UniFi OS platforms to version 5.1.19 or later. This is the vendor-recommended fix for the disclosed UniFi OS vulnerabilities, including CVE-2026-54403. Affected self-hosted servers, consoles, storage appliances, and EF-Core deployments should be updated to the corresponding patched release level provided by the vendor.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.