CVE-2008-2232 in afuse
Summary
by MITRE
The expand_template function in afuse.c in afuse 0.2 allows local users to gain privileges via shell metacharacters in a pathname.
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Analysis
by VulDB Data Team • 08/14/2019
The vulnerability identified as CVE-2008-2232 resides within the afuse 0.2 file system implementation, specifically within the expand_template function located in the afuse.c source file. This flaw represents a classic command injection vulnerability that arises from insufficient input validation and sanitization of user-provided pathnames. The afuse utility operates as a FUSE (Filesystem in Userspace) implementation that allows users to create virtual file systems, and the expand_template function serves to process template strings that may contain special characters for pathname expansion. When local users provide pathnames containing shell metacharacters such as semicolons, ampersands, or backticks, these characters are not properly escaped or filtered before being processed by the underlying shell commands, creating an avenue for arbitrary command execution.
The technical exploitation of this vulnerability occurs through the improper handling of user-supplied input within the template expansion mechanism. When a pathname containing shell metacharacters is processed by the expand_template function, these characters are interpreted by the shell as command separators or operators, allowing attackers to inject additional commands that execute with the privileges of the afuse process. This privilege escalation occurs because the afuse utility typically runs with elevated permissions to manage file system operations, and the shell command execution inherits these elevated privileges. The vulnerability falls under CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, and more broadly aligns with CWE-20, which covers improper input validation in software applications. The ATT&CK framework categorizes this as a privilege escalation technique through command injection, specifically under T1068, which involves exploiting vulnerabilities to gain higher-level privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially compromise the entire system integrity when the afuse utility is used in environments where users might have write access to file system paths. Attackers can leverage this vulnerability to execute arbitrary code, potentially gaining root access or elevating their privileges to the highest levels available to the afuse process. The attack vector is particularly concerning because it requires only local user access, making it accessible to any user who can interact with the afuse file system. This vulnerability could be exploited in scenarios where afuse is used in multi-user environments or when the utility is configured to run with elevated privileges, such as when managing system-level file operations or when integrated with other security-sensitive applications. The exploitation process typically involves crafting a malicious pathname that contains shell metacharacters, which then gets processed by the vulnerable expand_template function, leading to unintended command execution.
Mitigation strategies for CVE-2008-2232 should focus on input validation and proper shell command construction. The most effective approach involves implementing strict input sanitization within the expand_template function to filter or escape shell metacharacters before they can be processed. This includes using parameterized commands or shell escaping functions that prevent metacharacter interpretation. Additionally, system administrators should ensure that afuse is not run with unnecessary elevated privileges and should consider implementing privilege separation techniques. The vulnerability demonstrates the critical importance of secure coding practices, particularly around shell command construction, and emphasizes the need for regular security audits of file system implementations. Organizations should also consider updating to newer versions of afuse that have addressed this vulnerability, as version 0.2 is outdated and likely contains other security weaknesses. The mitigation approach aligns with security best practices outlined in NIST SP 800-160 and ISO 27001, which emphasize secure coding principles and input validation to prevent command injection attacks.