CVE-2011-1095 in C Library
Summary
by MITRE
locale/programs/locale.c in locale in the GNU C Library (aka glibc or libc6) before 2.13 does not quote its output, which might allow local users to gain privileges via a crafted localization environment variable, in conjunction with a program that executes a script that uses the eval function.
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Analysis
by VulDB Data Team • 12/28/2024
The vulnerability described in CVE-2011-1095 resides within the GNU C Library's locale handling mechanisms, specifically in the locale/programs/locale.c file. This flaw represents a classic privilege escalation vector that exploits the insecure processing of localization environment variables. The issue affects glibc versions prior to 2.13, making it a significant concern for systems running older versions of the GNU C Library. The vulnerability operates through a sophisticated attack chain that combines environmental manipulation with shell script execution patterns.
The technical flaw stems from the improper quoting of output generated by the locale program when processing localization environment variables. When a program processes locale data without proper shell escaping or quoting, it creates an environment where maliciously crafted localization variables can inject arbitrary commands into shell contexts. This occurs because the locale program's output is directly consumed by shell evaluation mechanisms, particularly those using the eval function, which executes strings as shell commands. The lack of proper output quoting means that special shell characters and metacharacters in locale data can be interpreted as shell syntax rather than literal text.
The operational impact of this vulnerability is substantial as it enables local users to escalate privileges on affected systems. An attacker can craft a malicious localization environment variable that, when processed by a vulnerable program, results in arbitrary code execution with elevated privileges. The attack requires a specific combination of conditions including a vulnerable glibc version, a program that executes shell scripts using eval, and the ability to set environment variables. This makes the vulnerability particularly dangerous in multi-user environments where local privilege escalation can lead to complete system compromise. The vulnerability aligns with CWE-78, which addresses improper neutralization of special elements used in shell commands, and follows attack patterns described in the MITRE ATT&CK framework under privilege escalation techniques.
Systems can be protected against this vulnerability through several mitigation strategies. The primary and most effective approach involves upgrading to glibc version 2.13 or later, which contains the necessary fixes for proper output quoting in locale processing. Additionally, system administrators should audit programs that use eval functions with environment variable data and implement proper shell escaping mechanisms. The principle of least privilege should be enforced by limiting the ability of local users to modify critical environment variables, particularly those related to localization. Organizations should also consider implementing security monitoring to detect unusual patterns in locale data processing and shell command execution. Regular security updates and patch management processes are essential to prevent exploitation of this and similar vulnerabilities in the GNU C Library ecosystem.