CyberSecBulletin
CVE-2026-34910Exploited in the wildNVD status: Analyzed

Ubiquiti UniFi OS Improper Input Validation

Published Updated By the CyberSecBulletin desk

CVE-2026-34910 is a critical-severity improper input validation vulnerability in UniFi OS Server from Ubiquiti, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 5.0.8 as the first without the flaw, so updating UniFi OS Server to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on June 23, 2026, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update UniFi OS Server to 5.0.8 or a later version.
  2. Update UDM to 5.1.12 or a later version.
  3. Update UDM-Pro to 5.1.12 or a later version.
  4. CISA's 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.
  5. Read the advisory on community.ui.com for workarounds and exact fixed builds.
  6. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
UbiquitiUniFi OS Serverbefore 5.0.85.0.8
UbiquitiUDMbefore 5.1.125.1.12
UbiquitiUDM-Probefore 5.1.125.1.12
UbiquitiUDM-SEbefore 5.1.125.1.12
UbiquitiUDM-Pro-Maxbefore 5.1.125.1.12
UbiquitiUDM-Beastbefore 5.1.115.1.11
UbiquitiEFGbefore 5.1.125.1.12
UbiquitiUDWbefore 5.1.125.1.12
UbiquitiUDRbefore 5.1.125.1.12
UbiquitiUDR7before 5.1.125.1.12
UbiquitiUDR-5Gbefore 5.1.125.1.12
UbiquitiExpress 7before 5.1.125.1.12
UbiquitiUNVRbefore 5.1.125.1.12
UbiquitiUNVR-Probefore 5.1.125.1.12
UbiquitiUNVR-Instantbefore 5.1.125.1.12
UbiquitiUNVR-G2before 5.1.125.1.12
UbiquitiUNVR-G2-Probefore 5.1.125.1.12
UbiquitiENVRbefore 5.1.125.1.12
UbiquitiENVR-Corebefore 5.1.125.1.12
UbiquitiUNAS-2before 5.1.105.1.10
UbiquitiUNAS-4before 5.1.105.1.10
UbiquitiUNAS-Probefore 5.1.105.1.10
UbiquitiUNAS-Pro-4before 5.1.105.1.10
UbiquitiUNAS-Pro-8before 5.1.105.1.10
UbiquitiUCKPbefore 5.1.125.1.12

Version data comes from the organisation that assigned the CVE; 35 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
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
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:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (hackerone.com).

Official description

A malicious actor with access to the network could exploit an Improper Input Validation vulnerability found in UniFi OS devices to execute a Command Injection.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Input Validation

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.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
  3. Added to CISA's Known Exploited Vulnerabilities catalogue.
  4. Deadline for US federal agencies to remediate, set by CISA.
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Technical write-ups (may include proof of concept)

Other vulnerabilities in UniFi OS Server

All UniFi OS Server vulnerabilities

Recent Improper Input Validation vulnerabilities

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