# CVE-2026-77539: Command injection in UniFi OS Server

> High-privilege network attackers can execute arbitrary commands on UniFi OS Server hosts via improper input validation.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** GHSA-2j95-j9fx-32w6

## What is CVE-2026-77539?

CVE-2026-77539 is a critical command injection vulnerability in Ubiquiti Inc UniFi OS Server, published on 26 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

A malicious actor with access to the network and high privileges could exploit an Improper Input Validation vulnerability found in UniFi OS Server to execute a Command Injection on the host device.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-77539?


## How do I fix CVE-2026-77539?

No fix has been published for CVE-2026-77539 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-77539 being exploited?

There is no known exploitation of CVE-2026-77539 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77539 and fix it if it is affected.

What it is: CVE-2026-77539 is a critical command injection vulnerability in Ubiquiti Inc UniFi OS Server, published on 26 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77539 in the wild and no public exploit code.

Affected product: Ubiquiti Inc UniFi OS Server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77539/ (Markdown: https://insights.sbomify.com/CVE-2026-77539/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77539
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77539
- OSV: https://osv.dev/vulnerability/CVE-2026-77539

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77539/
Summaries are generated and may contain mistakes; the official description above is the record.