UBB-XG: Improper Neutralization of Special Elements used in a Command
CVE-2026-21638 is a high-severity improper neutralization of special elements used in a command vulnerability in UBB-XG from Ubiquiti, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. The record lists version 1.2.3 as the first without the flaw, so updating UBB-XG to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.43% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update UBB-XG to 1.2.3 or a later version.
- Update UDB-Pro/UDB-Pro-Sector to 1.4.2 or a later version.
- Update UBB to 3.1.7 or a later version.
- Read the advisory on community.ui.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Ubiquiti | UBB-XG | before 1.2.3 | 1.2.3 |
| Ubiquiti | UDB-Pro/UDB-Pro-Sector | before 1.4.2 | 1.4.2 |
| Ubiquiti | UBB | before 3.1.7 | 3.1.7 |
| UI | Ubb-xg Firmware | before 1.2.3 | 1.2.3 |
| UI | Udb-pro Firmware | before 1.4.2 | 1.4.2 |
| UI | Udb-pro-sector Firmware | before 1.4.2 | 1.4.2 |
| UI | Ubb Firmware | before 3.1.7 | 3.1.7 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- AdjacentThe attacker must be on the same local network segment.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (hackerone.com).
Official description
A malicious actor in Wi-Fi range of the affected product could leverage a vulnerability in the airMAX Wireless Protocol to achieve a remote code execution (RCE) within the affected product. Affected Products: UBB-XG (Version 1.2.2 and earlier) UDB-Pro/UDB-Pro-Sector (Version 1.4.1 and earlier) UBB (Version 3.1.5 and earlier) Mitigation: Update your UBB-XG to Version 1.2.3 or later. Update your UDB-Pro/UDB-Pro-Sector to Version 1.4.2 or later. Update your UBB to Version 3.1.7 or later.
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
Recent Improper Neutralization of Special Elements used in a Command vulnerabilities
- 9.0 Critical severity
- 9.1 Critical severity
- 9.1 Critical severity
- 8.1 High severity
- 10.0 Critical severity
- 9.8 Critical severity
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