CVE-2026-34909 — UniFi OS Server
CRITICALCVE-2026-34909 is a critical-severity (CVSS 10) Path Traversal vulnerability in Ubiquiti Inc UniFi OS Server. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-06-23) — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
A malicious actor with access to the network could exploit a Path Traversal vulnerability found in UniFi OS devices to access files on the underlying system that could be manipulated…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-06-23. Federal agencies were required to remediate by 2026-06-26.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-34909.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Description
A malicious actor with access to the network could exploit a Path Traversal vulnerability found in UniFi OS devices to access files on the underlying system that could be manipulated to access an underlying account.
Affected Products
UniFi OS ServerUbiquiti IncExpressUbiquiti IncUDMUbiquiti IncUDM-ProUbiquiti IncUDM-SEUbiquiti IncUDM-Pro-MaxUbiquiti IncDetection & mitigation playbook
Vendor / applianceDetect
Inventory every Ubiquiti Inc UniFi OS Server deployment and check each version against the affected-products list above.
Fix
Apply the Ubiquiti Inc UniFi OS Server security patch or hotfix for CVE-2026-34909 on the affected version, following the vendor advisory for your exact build.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
Frequently Asked Questions
Is CVE-2026-34909 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.