CVE-2026-34910
CVE-2026-34910 is a security flaw in Ubiquiti UniFi OS, networking equipment for homes and offices. Attackers can run commands on Ubiquiti UniFi OS. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 23 Jun 2026.[1]
Ubiquiti UniFi OS is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version 5.0.8, 5.1.12 and 5.1.11.
Description
CISA calls it an improper input validation in Ubiquiti UniFi OS. In its words: “Ubiquiti UniFi OS contains an improper input validation vulnerability which could allow a malicious actor with access to the network to conduct command injection.”[1]
The underlying weakness is improper input validation (CWE-20), in MITRE’s list of common software weaknesses.[2]
It scores 10.0 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| UniFi OS Server | 5.0.8 |
| UDM | 5.1.12 |
| UDM-Pro | 5.1.12 |
| UDM-SE | 5.1.12 |
| UDM-Pro-Max | 5.1.12 |
| UDM-Beast | 5.1.11 |
| EFG | 5.1.12 |
| UDW | 5.1.12 |
Most families won’t have Ubiquiti UniFi OS; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 23 Jun 2026, 32 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 26 Jun 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 90%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Ubiquiti has published a fix or advice.[3] 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).”[1]
- Check whether you use it.Ubiquiti UniFi OS is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 5.0.8, 5.1.12 and 5.1.11), or not in use. CISA gave US government agencies until 26 Jun 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 10.0.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 90%.[4] |
See also
Other Ubiquiti UniFi OS flaws
- CVE-2026-34909: path traversal ·
- CVE-2026-34908: improper access control ·
Other Ubiquiti flaws
- CVE-2010-5330, Ubiquiti AirOS: command injection ·
Other improper input validation flaws
- CVE-2026-93952, Arista VeloCloud Orchestrator: improper input validation ·
- CVE-2019-1068, Microsoft SQL Server: remote code execution ·
- CVE-2026-12569, PTC Windchill and FlexPLM: improper input validation ·
- CVE-2026-6973, Ivanti Endpoint Manager Mobile (EPMM): improper input validation ·
- CVE-2026-34197, Apache ActiveMQ: improper input validation ·
Added the same day
- CVE-2026-34909, Ubiquiti UniFi OS: path traversal ·
- CVE-2026-34908, Ubiquiti UniFi OS: improper access control ·
- CVE-2025-67038, Lantronix EDS5000: code injection ·
Every Ubiquiti flaw on CISA’s list · Everything added in June 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Ubiquiti UniFi OS Improper Input Validation Vulnerability”. Known Exploited Vulnerabilities Catalog, added 23 Jun 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-34910 Detail”. National Vulnerability Database, published 22 May 2026.
- ^ Ubiquiti. Advisories and fixes: community.ui.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.900, percentile 99.8, 31 Oct 2026.
- CVE Program. “CVE-2026-34910”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.