Ubuntu-Pro-Client Root Priv Escalation via APT Source Injection
CVE-2026-11386 Published on July 16, 2026
ubuntu-pro-client Input Validation Vulnerability Leading to Arbitrary APT Directive Injection and Remote Code Execution
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[] fieldwhich is passed positionally into a root-executed apt-get install commandan 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.
Vulnerability Analysis
CVE-2026-11386 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Weakness Type
Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
Affected Versions
Canonical ubuntu-pro-client (ubuntu-advantage-tools):- Before 37.3 is affected.
- Version 37.2ubuntu0.1 is unaffected.
- Version 37.2ubuntu~24.04.1 is unaffected.
- Version 37.2ubuntu~22.04.1 is unaffected.
- Version 37.1ubuntu0~20.04.1 is unaffected.
- Version 37.1ubuntu0~18.04.1 is unaffected.
- Version 37.1ubuntu0~16.04.1 is unaffected.
- Version 19.7ubuntu0.1 is unaffected.