CVE-2026-102371 in Ubuntu Pro for WSL
Summary
by MITRE • 09/29/2026
In wsl-pro-service before 0.1.19ubuntu3, the service component which runs as root inside each WSL instance attaches the instance to Ubuntu Pro by executing the pro client with the Ubuntu Pro token passed as a command-line argument (pro attach <token>). On systems where /proc is mounted without process-hiding mitigations (such as hidepid), which is the default in WSL, an unprivileged local user or process in the same WSL instance can read the token from /proc/<pid>/cmdline while the attach process is running. The leaked token could then be used to attach other machines to the victim's Ubuntu Pro subscription and gain unauthorized access to Ubuntu Pro services.
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Analysis
by VulDB Data Team • 09/29/2026
The vulnerability identified in wsl-pro-service prior to version 0.1.19ubuntu3 represents a critical information disclosure flaw rooted in improper handling of sensitive credentials within command-line arguments during service initialization. The core technical issue arises from the architectural decision to pass the Ubuntu Pro authentication token directly as an argument when invoking the pro client utility via the command line, specifically through the execution of pro attach with the token provided inline. This approach exposes the secret material to any process capable of inspecting the operating system's process metadata, rather than utilizing more secure mechanisms such as environment variables or configuration files with restricted permissions that are not visible in standard process listings.
The exploitation vector relies heavily on the default configuration of the Linux Subsystem for Windows (WSL) regarding the /proc filesystem mount options. In typical WSL deployments, the /proc filesystem is mounted without applying hidepid mitigations, which means it operates under a visibility model where all processes within the same instance can view detailed information about every other process running in that namespace. Consequently, when wsl-pro-service executes with root privileges to attach the system to Ubuntu Pro, the command line containing the plaintext token becomes accessible via /proc/<pid>/cmdline for any unprivileged local user or malicious process operating within the same WSL instance. This lack of isolation allows a lower-privilege entity to read the memory and command-line arguments of higher-privilege processes without requiring additional privilege escalation exploits, effectively bypassing standard access controls through passive observation of system state.
The operational impact of this vulnerability is significant as it compromises the integrity and exclusivity of Ubuntu Pro subscriptions. An attacker who successfully extracts the token can utilize it to authenticate against Ubuntu Pro services from external systems or other instances not authorized under that subscription. This unauthorized usage leads directly to financial loss for the subscriber due to potential overage charges or quota exhaustion, while also enabling the attacker to access premium security updates and compliance features intended only for legitimate users. Furthermore, this exposure undermines trust in the automatic service management components of WSL, as it demonstrates a failure to protect high-value credentials during routine administrative operations that are performed with elevated privileges.
From a classification perspective, this flaw aligns closely with CWE-78 Improper Neutralization of Special Elements used in an OS Command and CWE-209 Generation of Error Message Containing Sensitive Information, as the sensitive data is exposed through standard system interfaces intended for process monitoring rather than secure credential storage. In terms of adversary tactics, this vulnerability facilitates Initial Access and Credential Access within the ATT&CK framework, specifically relating to techniques involving command-line interface discovery and exploitation of local information leaks. The attack pattern mirrors common Linux privilege escalation paths where attackers leverage world-readable or group-readable /proc entries to harvest secrets from daemons running with higher permissions than their own.
Mitigation strategies must focus on eliminating the exposure surface for sensitive tokens during process execution. The primary remediation involves updating wsl-pro-service to version 0.1.19ubuntu3 or later, where the developers have addressed this by avoiding the passing of tokens via command-line arguments. Instead, secure implementations should utilize environment variables which are not visible in /proc/<pid>/cmdline, or write the token to a temporary file with restrictive permissions that is deleted immediately after use. Additionally, system administrators can apply mitigations at the operating system level by mounting /proc with hidepid=2 options if supported and appropriate for their security posture, although this may impact compatibility with certain WSL features. Ensuring that service components do not expose secrets in process metadata remains a fundamental requirement for maintaining confidentiality in multi-user Linux environments.