UniFi OS Server: Improper Neutralization of Special Elements used in a Command
CVE-2026-54402 is a high-severity improper neutralization of special elements used in a command vulnerability in UniFi OS Server from Ubiquiti, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 5.1.19 as the first without the flaw, so updating UniFi OS Server to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 1.76% chance of exploitation within 30 days, higher than 78% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update UniFi OS Server to 5.1.19 or a later version.
- Update Dream Machines to 5.1.19 or a later version.
- Update Enterprise Fortress Gateway to 5.1.19 or a later version.
- Read the advisory on community.ui.com for workarounds and exact fixed builds.
Affected products and versions
Version data comes from the organisation that assigned the CVE; 18 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.9 | Critical | CNA (hackerone.com) |
| CVSS 3.1 | 8.8 | High | NVD |
Official description
A malicious actor with access to the network and low privileges could exploit an Improper Input Validation vulnerability found in UniFi OS to execute a Command Injection on the host device.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements used in a Command
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.
How developers prevent this class of flaw
- If at all possible, use library calls rather than external processes to recreate the desired functionality.
- If possible, ensure that all external commands called from the program are statically created.
- Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.
More Improper Neutralization of Special Elements used in a Command vulnerabilities (CWE-77)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in UniFi OS Server
- 10.0 Critical severity
- 9.0 Critical severity
- 9.0 Critical severity
- 9.1 Critical severity
- 9.1 Critical severity
- 9.9 Critical severity
Recent Improper Neutralization of Special Elements used in a Command vulnerabilities
- 7.2 High severity
- 8.8 High severity
- 8.7 High severity
- 7.3 High severity
- 9.9 Critical severity
- 7.5 High severity
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