# CVE-2026-11386: ubuntu-pro-client Input Validation Vulnerability Leading to Arbitrary APT Directive Injection and Remote Code Execution

> Attacker can inject APT directives via contract server response to install malicious packages and execute code as root on Ubuntu systems.

- **Severity:** Critical 9.0 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Jul 2026
- **Updated:** 16 Jul 2026
- **Also known as:** GHSA-9836-vm3x-qwmj, UBUNTU-CVE-2026-11386

## What is CVE-2026-11386?

CVE-2026-11386 is a critical command injection vulnerability in Canonical Ubuntu 14.04 LTS, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An input validation and injection vulnerability exists in Canonical ubuntu-pro-client (formerly ubuntu-advantage-tools). The client constructs APT source files (such as /etc/apt/sources.list.d/ubuntu-.list or their DEB822 equivalents) using data received directly from the contract server response via the directives.suites[] and directives.aptURL fields. Because the client utilizes Python's str.format() to write these files without performing escaping, validation, or newline character filtering, a malicious or tampered contract response containing embedded newline (\n) characters can successfully inject arbitrary, attacker-controlled deb configuration lines into root-owned APT sources. When combined with the unvalidated additionalPackages[] field—which is passed positionally into a root-executed apt-get install command—an attacker capable of spoofing or manipulating the contract response (e.g., via a compromised internal infrastructure, an intercepted connection utilizing a trusted CA, or local logical bugs) can force the client to fetch and install malicious packages. This ultimately leads to arbitrary code execution with root privileges on the affected system. This component is preinstalled on supported Ubuntu Server releases and auto-attaches by default on cloud provider Ubuntu Pro images.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-11386?


## How do I fix CVE-2026-11386?

Apply the vendor's patch.

## Is CVE-2026-11386 being exploited?

There is no known exploitation of CVE-2026-11386 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11386 and fix it if it is affected.

What it is: CVE-2026-11386 is a critical command injection vulnerability in Canonical Ubuntu 14.04 LTS, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-11386 in the wild and no public exploit code.

Affected product: Canonical Ubuntu 14.04 LTS. 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-2026-11386/ (Markdown: https://insights.sbomify.com/CVE-2026-11386/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11386
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11386
- OSV: https://osv.dev/vulnerability/CVE-2026-11386

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-11386/
Summaries are generated and may contain mistakes; the official description above is the record.