CVE-2004-2264 in less
Summary
by MITRE
** DISPUTED ** Format string bug in the open_altfile function in filename.c for GNU less 382, 381, and 358 might allow local users to cause a denial of service or possibly execute arbitrary code via format strings in the LESSOPEN environment variable. NOTE: since less is not setuid or setgid, then this is not a vulnerability unless there are plausible scenarios under which privilege boundaries could be crossed.
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Analysis
by VulDB Data Team • 08/08/2024
The vulnerability described in CVE-2004-2264 represents a format string bug within the GNU less utility, specifically in the open_altfile function located in filename.c. This flaw affects versions 382, 381, and 358 of the less program, which is a widely used pager utility for viewing text files in Unix-like operating systems. The vulnerability manifests when the LESSOPEN environment variable contains format specifiers that are improperly handled during string processing. According to CWE-134, this issue falls under the category of format string vulnerabilities where untrusted input is used as a format string argument to functions like printf or fprintf without proper validation or sanitization.
The technical exploitation of this vulnerability occurs through the manipulation of the LESSOPEN environment variable, which is designed to specify alternative files to be opened when less encounters certain file types. When a local user sets this variable to contain format specifiers such as %x, %s, or %n, the open_altfile function processes these strings without adequate protection against format string interpretation. This creates a potential privilege escalation path or denial of service condition, as the format string can cause the program to read from arbitrary memory locations or attempt to write to memory addresses specified by the attacker. The ATT&CK framework categorizes this under T1068, privilege escalation, when the vulnerability is exploited in contexts where privilege boundaries might be crossed.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it could potentially enable arbitrary code execution under specific conditions. While the vulnerability is disputed due to less not being setuid or setgid, the assessment must consider scenarios where privilege boundaries could be crossed through other means. The vulnerability's severity is heightened when less is executed in environments where users might have the ability to influence the execution context, such as in shared or restricted environments. The lack of proper input validation in the filename.c module creates a condition where attacker-controlled data can influence program execution flow and memory access patterns, potentially leading to unauthorized privilege escalation or system compromise.
Mitigation strategies for CVE-2004-2264 should focus on input validation and proper string handling practices. The most effective approach involves ensuring that environment variables like LESSOPEN are properly sanitized before being used in format string operations. This includes implementing proper bounds checking, using secure string formatting functions such as snprintf instead of sprintf, and avoiding direct use of user-controllable data as format specifiers. System administrators should also consider implementing proper environment variable restrictions and monitoring for unusual LESSOPEN values that might indicate attempted exploitation. Additionally, the vulnerability highlights the importance of secure coding practices in utility programs and the need for regular security audits of widely deployed system tools. The vulnerability serves as a reminder of the critical importance of format string security in Unix-like systems where utilities often handle untrusted input from multiple sources.