Security readout for executives and security teams
Plain-English summary
UniFi OS Server may allow a network-connected attacker who already has high privileges to inject commands into the underlying host. Successful exploitation could compromise sensitive data, alter systems, or disrupt service. The supplied CVSS score is 9.1, but the exact affected version range is unclear.
Executive priority
Treat as an urgent validation and remediation task because successful exploitation can compromise the host with high impact. Prioritize internet-accessible or broadly reachable management deployments, while recognizing that exploitation requires high privileges and active exploitation is not established.
Technical view
CVE-2026-77539 is an improper input validation flaw (CWE-20) resulting in host command injection. Its CVSS 3.1 vector indicates network reachability, low attack complexity, high privileges, no user interaction, changed scope, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure requires UniFi OS Server, network access to the vulnerable interface, and high privileges. The source lists version "0" while marking other versions unaffected by default, so the actionable affected range cannot be established confidently from this bundle.
Exploitation context
The supplied record does not show a CISA KEV listing or other evidence of active exploitation. Exploitation nevertheless requires an already highly privileged actor and could extend compromise from the application into the host device.
Researcher notes
The public bundle supports the vulnerability class, prerequisites, impact, and CVSS rating, but its version data is ambiguous. No patch version, technical root cause, affected endpoint, indicators, or exploitation evidence is provided here. Consult the cited vendor advisory before making version-specific decisions.
Mitigation direction
- Review Ubiquiti Security Advisory Bulletin 067 for confirmed affected versions and vendor remediation.
- Apply the vendor-recommended update or mitigation after validating compatibility and operational impact.
- Restrict UniFi OS Server access to trusted management networks and authorized administrators.
- Review privileged accounts and revoke unnecessary, stale, or compromised access.
Validation and detection
- Inventory all UniFi OS Server deployments and record their exact installed versions.
- Compare installed versions with the affected range stated in Ubiquiti's advisory.
- Confirm management interfaces are unreachable from untrusted networks.
- Review logs for unexpected privileged activity, configuration changes, or host-level command execution.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-20: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-77539 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H2.36UbiquitiVulnerability scoring details
Base CVSS 3.1 score
9.1CriticalVector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://community.ui.com/releases/Security-Advisory-Bulletin-067/fc4a3488-7c43-4628-8bab-f715e96dbfc9CVE reference, Ubiquiti
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.