CVE-2026-34909: Ubiquiti UniFi OS Path Traversal Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Ubiquiti UniFi OS. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-06-23, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-06-26; treat that as the outer limit, not the target.
• EPSS 1.8%, percentile 78: FIRST’s model estimates a 1.8% chance of exploitation activity in the next 30 days, higher than 78% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.

What it is

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.

CISA’s summary

Ubiquiti UniFi OS contains a path traversal vulnerability which could allow a malicious actor with access to the network to access files on the underlying system that could be manipulated to access an underlying account.

Weakness type: CWE-22.

Product: Ubiquiti UniFi OS · Assigned by: hackerone · Published: 2026-05-22

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2026-06-23; federal due date 2026-06-26. Known ransomware use: Unknown.
• CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
• CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 1.79% probability of exploitation activity in the next 30 days; percentile 78.

Timeline

• 2026-05-22 — CVE record published by hackerone
• 2026-06-23 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2026-06-24 — CVE record last updated
• 2026-06-26 — CISA remediation deadline for US federal agencies

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (community.ui.com) community.ui.com

Vulnerability records

1. CVE.org record CVE-2026-34909 cve.org
2. NVD entry CVE-2026-34909 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov
2. Listed in CISA KEV notes (cisa.gov) cisa.gov
3. Listed in CISA KEV notes (cisa.gov) cisa.gov

Other references from the CVE record and advisory

1. pwndefend.com pwndefend.com

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