CVE-2026-9494: ubuntu-pro-client Information Disclosure via Cleartext Bearer Token Exposure in Process Command Line

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-16 · updated 2026-07-16
Weakness: CWE-214

Description

An information disclosure vulnerability exists in Canonical ubuntu-pro-client (formerly ubuntu-advantage-tools). The client validates Ubuntu Pro APT credentials by executing /usr/lib/apt/apt-helper using the download-file command. During this process, the secret bearer token is embedded directly in the cleartext URL component passed via the command-line arguments (argv), resulting in a URL format such as https://bearer:<token>@esm.ubuntu.com/.../. On systems utilizing a default-mounted /proc file system where process-hiding mitigations (such as hidepid) are disabled, an unprivileged local attacker can monitor system processes and read the sensitive bearer token directly from /proc/cmdline while the helper process is actively running. This leaked token can subsequently be used to gain unauthorized access to the victim's Ubuntu Pro or Expanded Security Maintenance (ESM) repositories.

Affected products

Canonical ubuntu-pro-client (ubuntu-advantage-tools): before 37.3 — fixed in 37.3
Canonical Ubuntu 14.04 LTS: all versions
Canonical Ubuntu 16.04 LTS: all versions
Canonical Ubuntu 18.04 LTS: all versions
Canonical Ubuntu 20.04 LTS: all versions
Canonical Ubuntu 22.04 LTS: all versions
Canonical Ubuntu 24.04 LTS: all versions
Canonical Ubuntu 26.04 LTS: all versions

How to fix

Upgrade to a fixed version: Canonical ubuntu-pro-client (ubuntu-advantage-tools) 37.3. Check the vendor advisory for mitigations.

References

https://ubuntu.com/security/CVE-2026-9494

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