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Fencer Intel
critical 9.0

CVE-2026-11386 json

ubuntu-pro-client Input Validation Vulnerability Leading to Arbitrary APT Directive Injection and Remote Code Execution

published 3mo ago modified 3mo ago also EUVD-2026-44911

cvss
9.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

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.

Patch / fix

  • Canonical ubuntu-pro-client (ubuntu-advantage-tools) 37.3
  • Canonical Ubuntu 26.04 LTS 37.2ubuntu0.1
  • Canonical Ubuntu 24.04 LTS 37.2ubuntu~24.04.1
  • Canonical Ubuntu 22.04 LTS 37.2ubuntu~22.04.1
  • Canonical Ubuntu 20.04 LTS 37.1ubuntu0~20.04.1
  • Canonical Ubuntu 18.04 LTS 37.1ubuntu0~18.04.1
  • Canonical Ubuntu 16.04 LTS 37.1ubuntu0~16.04.1
  • Canonical Ubuntu 14.04 LTS 19.7ubuntu0.1
  • ubuntu-advantage-tools Ubuntu 22.04 LTS 37.2ubuntu~22.04.1
  • ubuntu-advantage-tools Ubuntu 24.04 LTS 37.2ubuntu~24.04.1
  • ubuntu-advantage-tools Ubuntu 26.04 LTS 37.2ubuntu0.1

ubuntu advisories UBUNTU-CVE-2026-11386

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
3mo ago

Exploit prediction

0.53% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 9.0 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

  • Canonical ubuntu-pro-client (ubuntu-advantage-tools)
  • Canonical Ubuntu 26.04 LTS
  • Canonical Ubuntu 24.04 LTS
  • Canonical Ubuntu 22.04 LTS
  • Canonical Ubuntu 20.04 LTS
  • Canonical Ubuntu 18.04 LTS
  • Canonical Ubuntu 16.04 LTS
  • Canonical Ubuntu 14.04 LTS

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.