CVE-2026-11386
NVD analysis in progress
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.
What this means
- Exposure
- Exploitable remotely over the network, without authentication and with no action from the victim. The attack does require particular conditions, which makes it less systematic.
- Impact
- An attacker can read sensitive data, modify or destroy data and take the service offline. The impact spreads beyond the vulnerable component into other parts of the system.
- Weakness
- The application accepts input without checking it, opening the door to unintended behaviour.
- Likelihood
- Its EPSS score stays low: nothing points to imminent exploitation, which is no reason to leave it unpatched.
What to doPatch without waiting for the next scheduled cycle. Start with the instances exposed to the internet.
Read automatically from the CVSS vector, the weakness type (CWE) and the EPSS score. The technical description above remains the one published by NIST.