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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-11386?
How do I fix CVE-2026-11386?
Apply the vendor's patch.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is CVE-2026-11386 being exploited?
There is no known exploitation of CVE-2026-11386 in the wild and no public exploit code.
Sources
Also known as GHSA-9836-vm3x-qwmj, UBUNTU-CVE-2026-11386.