9.1

CVE-2026-77539: ubiquiti inc unifi os server Improper Input Validation

CVSS: 9.1v3.1CriticalDeferred
Published 26-08-2026Last modified 27-08-2026
Open JSON

Vulnerability summary

CVE-2026-77539 is a critical (CVSS 9.1) Improper Input Validation vulnerability in ubiquiti inc unifi os server. EPSS estimates a 1.29% chance of exploitation in the next 30 days, higher than 69.8% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.1/10
010
Critical · v3.1 (CVE.org)
EPSS score
1.29%
0%100%
Low · +0.48 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 26-08-2026
    PublishedVulnerability first disclosed.
  2. 27-08-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

1.29%

Chance of exploitation in the next 30 days

Percentile

70%

Versus all other CVEs

30-day change

+0.48 pp

From 0.81% on 19-09-2026

19-09-202619-10-2026
EPSS score
1.29%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Ubiquiti inc1 product

1 vendor · 1 product

References

1 links