Ubiquiti UniFi OS Server up to 5.1.36 input validation

Summaryinfo

A vulnerability, which was classified as very critical, has been found in Ubiquiti UniFi OS Server up to 5.1.36. This vulnerability affects unknown code. Performing a manipulation results in input validation. This vulnerability is cataloged as CVE-2026-77539. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability classified as very critical has been found in Ubiquiti UniFi OS Server up to 5.1.36. This affects an unknown functionality. The manipulation with an unknown input leads to a input validation vulnerability. CWE is classifying the issue as CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

A malicious actor with access to the network and high privileges could exploit an Improper Input Validation vulnerability found in UniFi OS Server to execute a Command Injection on the host device.

It is possible to read the advisory at community.ui.com. This vulnerability is uniquely identified as CVE-2026-77539 since 08/20/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Additional levels of successful authentication are needed for exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/27/2026).

Upgrading to version 5.1.37 eliminates this vulnerability.

The vulnerability is also documented in the databases at EUVD (EUVD-2026-66366) and CERT Bund (WID-SEC-2026-3028). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Ubiquiti UniFi

Productinfo

Vendor

• Ubiquiti

Name

• UniFi OS Server

Version

• 5.1.0
• 5.1.1
• 5.1.2
• 5.1.3
• 5.1.4
• 5.1.5
• 5.1.6
• 5.1.7
• 5.1.8
• 5.1.9
• 5.1.10
• 5.1.11
• 5.1.12
• 5.1.13
• 5.1.14
• 5.1.15
• 5.1.16
• 5.1.17
• 5.1.18
• 5.1.19
• 5.1.20
• 5.1.21
• 5.1.22
• 5.1.23
• 5.1.24
• 5.1.25
• 5.1.26
• 5.1.27
• 5.1.28
• 5.1.29
• 5.1.30
• 5.1.31
• 5.1.32
• 5.1.33
• 5.1.34
• 5.1.35
• 5.1.36

License

• commercial

CPE 2.3info

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CPE 2.2info

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Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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