CVE-2011-1020 in Linux
Summary
by MITRE
The proc filesystem implementation in the Linux kernel 2.6.37 and earlier does not restrict access to the /proc directory tree of a process after this process performs an exec of a setuid program, which allows local users to obtain sensitive information or cause a denial of service via open, lseek, read, and write system calls.
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Analysis
by VulDB Data Team • 09/02/2024
The vulnerability described in CVE-2011-1020 represents a critical access control flaw within the Linux kernel's proc filesystem implementation affecting versions 2.6.37 and earlier. This issue stems from improper handling of process permissions during the exec system call sequence when a setuid program is executed. The fundamental problem occurs because the kernel fails to properly revoke access permissions to the /proc directory tree of a process immediately following an exec operation that involves setuid binaries, creating a window where malicious local users can exploit this inconsistency.
The technical flaw manifests when a process executes a setuid program, which should typically result in a complete reset of the process's security context and associated access controls. However, the kernel's proc filesystem implementation maintains access permissions to the process's /proc entries, allowing attackers to perform various system calls including open, lseek, read, and write operations against the target process's proc entries. This creates a scenario where sensitive information that should be restricted to the process owner or privileged users becomes accessible to local attackers who can leverage these capabilities to extract process memory contents, environment variables, or other confidential data.
The operational impact of this vulnerability extends beyond simple information disclosure to include potential denial of service conditions and privilege escalation opportunities. Attackers can exploit this weakness to gather sensitive process information such as memory mappings, file descriptor contents, and process-specific data that could aid in further exploitation attempts. The ability to perform read and write operations against proc entries of setuid processes particularly threatens system integrity, as it may enable attackers to manipulate process behavior or inject malicious data into process memory spaces. This vulnerability directly violates the principle of least privilege and creates persistent access vectors that persist even after legitimate setuid execution contexts have been established.
From a cybersecurity perspective, this vulnerability maps to CWE-276, which addresses improper privileges, and aligns with ATT&CK techniques focusing on privilege escalation and information gathering. The flaw represents a classic case of inadequate access control enforcement in kernel space, where the security boundaries between different process contexts become blurred. Organizations affected by this vulnerability should implement immediate mitigations including kernel updates to versions 2.6.38 or later where the issue has been resolved, along with monitoring for suspicious proc filesystem access patterns and implementing additional security controls such as mandatory access controls or process isolation measures. The vulnerability demonstrates the critical importance of proper privilege management in kernel implementations and highlights the need for comprehensive security testing of system call interfaces that handle sensitive process information.