CVE-2017-5226 in Bubblewrap
Summary
by MITRE
When executing a program via the bubblewrap sandbox, the nonpriv session can escape to the parent session by using the TIOCSTI ioctl to push characters into the terminal's input buffer, allowing an attacker to escape the sandbox.
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Analysis
by VulDB Data Team • 07/26/2025
The vulnerability identified as CVE-2017-5226 resides within the bubblewrap sandboxing mechanism, a security tool designed to isolate untrusted programs from the host system. This flaw represents a critical sandbox escape vulnerability that undermines the fundamental security assumptions of containerized execution environments. The issue specifically affects the nonpriv session functionality of bubblewrap, which operates under the principle of reduced privileges to prevent malicious code from accessing sensitive system resources. When a program executes through this sandboxed environment, the vulnerability allows an attacker to manipulate terminal input buffers through improper privilege handling.
The technical exploitation of this vulnerability leverages the TIOCSTI ioctl command, a terminal input control mechanism that normally requires elevated privileges to execute. In the affected bubblewrap implementation, the nonpriv session fails to properly validate or restrict access to this ioctl function, enabling malicious processes to inject characters directly into the terminal input buffer of the parent session. This occurs because the sandbox does not adequately separate the terminal input handling between the isolated environment and the host system, creating an unintended communication channel that bypasses normal security boundaries. The TIOCSTI command specifically allows pushing characters into a terminal's input queue, which when abused can enable command injection attacks.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the security model of the entire sandboxing architecture. Attackers can leverage this escape mechanism to execute arbitrary commands with the privileges of the parent session, potentially gaining access to sensitive data, system resources, or other running processes. The vulnerability is particularly dangerous in multi-user environments where sandboxed applications might be running with elevated privileges or where the parent session has access to restricted resources. This escape vector can be exploited in various scenarios including web browsers running sandboxed plugins, email clients processing untrusted attachments, or any application that relies on bubblewrap for security isolation.
This vulnerability maps directly to CWE-284, which describes improper access control in software systems, and aligns with ATT&CK technique T1068, which covers local privilege escalation through system manipulation. The attack pattern follows a typical sandbox escape methodology where an attacker leverages kernel-level functionality to break out of restricted environments. Security researchers have noted that such vulnerabilities often stem from insufficient input validation and improper privilege separation in system call interfaces, particularly affecting containerization and sandboxing technologies. The remediation typically involves implementing stricter ioctl access controls, proper privilege separation between sessions, and comprehensive input validation for terminal manipulation commands.
Organizations utilizing bubblewrap or similar sandboxing technologies must immediately implement mitigations including kernel updates that restrict TIOCSTI access, privilege separation hardening, and comprehensive security audits of sandboxed applications. The vulnerability demonstrates the critical importance of maintaining strict boundaries between isolated execution environments and host systems, as even minor privilege leakage can result in complete system compromise. System administrators should also consider implementing additional monitoring for unusual terminal input patterns and ensure that all sandboxed applications undergo rigorous security testing before deployment in production environments.