CVE-2016-10122 in Firejail
Summary
by MITRE
Firejail does not properly clean environment variables, which allows local users to gain privileges.
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Analysis
by VulDB Data Team • 08/30/2020
The vulnerability identified as CVE-2016-10122 resides within Firejail, a security sandboxing tool designed to restrict application access and limit potential damage from compromised applications. This flaw represents a critical privilege escalation vulnerability that undermines the fundamental security model of the sandboxing mechanism. Firejail operates by creating isolated environments for applications, preventing them from accessing system resources or other processes. However, the improper handling of environment variables creates an exploitable condition that allows local attackers to bypass these security boundaries and elevate their privileges.
The technical flaw manifests in Firejail's failure to properly sanitize or reset environment variables during the sandbox initialization process. When applications are executed within a Firejail sandbox, the tool should ensure that no potentially malicious environment variables from the parent process carry over into the restricted environment. This oversight enables attackers to inject malicious values into environment variables that Firejail does not properly clean, creating opportunities for exploitation. The vulnerability specifically affects how Firejail manages variables such as PATH, LD_PRELOAD, and other critical environment parameters that influence program execution behavior.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the security assurances provided by Firejail's sandboxing capabilities. Local users who can execute arbitrary code within the restricted environment can leverage this flaw to gain elevated privileges, potentially allowing them to execute commands with root permissions. This represents a severe regression in the security model since the primary purpose of sandboxing is to contain potential threats and prevent privilege escalation. The vulnerability affects systems where Firejail is used to run untrusted applications, making it particularly dangerous in multi-user environments or when Firejail is employed as a security control in production systems.
Security researchers have classified this vulnerability according to CWE-200, which addresses "Information Exposure," and CWE-264, covering "Permissions, Privileges, and Access Controls." The flaw aligns with ATT&CK technique T1068, "Exploitation for Privilege Escalation," demonstrating how improper environment variable handling can be exploited to gain elevated system access. Organizations utilizing Firejail for security isolation should consider this vulnerability as a critical concern, particularly in environments where untrusted applications are executed or where Firejail serves as a primary security control. The vulnerability underscores the importance of proper environment variable sanitization in security tools and highlights the potential consequences when such sanitization fails. Mitigation efforts should include immediate patching of Firejail installations and implementation of additional monitoring to detect potential exploitation attempts.