CVE-2011-1071 in C Library
Summary
by MITRE
The GNU C Library (aka glibc or libc6) before 2.12.2 and Embedded GLIBC (EGLIBC) allow context-dependent attackers to execute arbitrary code or cause a denial of service (memory consumption) via a long UTF8 string that is used in an fnmatch call, aka a "stack extension attack," a related issue to CVE-2010-2898, CVE-2010-1917, and CVE-2007-4782, as originally reported for use of this library by Google Chrome.
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Analysis
by VulDB Data Team • 10/11/2024
The vulnerability identified as CVE-2011-1071 represents a critical stack extension attack affecting the GNU C Library (glibc) and Embedded GLIBC (EGLIBC) versions prior to 2.12.2. This flaw specifically manifests when processing long UTF8 strings within fnmatch function calls, creating a condition where attackers can manipulate memory allocation patterns to either execute arbitrary code or induce denial of service through excessive memory consumption. The vulnerability operates at the intersection of character encoding handling and stack management, exploiting the way these libraries process pattern matching operations with Unicode input.
The technical mechanism underlying this vulnerability involves the fnmatch function's handling of UTF8 encoded strings that exceed normal processing limits. When glibc encounters extended UTF8 sequences during pattern matching, the internal buffer management and stack allocation routines can be manipulated to cause unintended memory expansion. This occurs because the library does not properly validate the length and structure of UTF8 input sequences before processing them through the fnmatch interface, leading to stack overflow conditions or excessive memory allocation that can be leveraged for privilege escalation or system instability. The vulnerability is classified under CWE-122 as improper restriction of operations within the bounds of a memory buffer, specifically manifesting as stack-based buffer overflow conditions.
The operational impact of CVE-2011-1071 extends across numerous system components that rely on glibc for pattern matching operations, including web browsers like Google Chrome, system utilities, and network services. Attackers can exploit this vulnerability by crafting malicious UTF8 strings that trigger the vulnerable code path, potentially leading to complete system compromise when executed in contexts with elevated privileges. The denial of service aspect presents a significant risk to service availability, as attackers can consume system memory resources to exhaustion, causing legitimate processes to fail. This vulnerability particularly affects systems where glibc is used for file pattern matching operations, shell command processing, or any application that interfaces with fnmatch functionality.
Mitigation strategies for CVE-2011-1071 require immediate patching of affected glibc versions to 2.12.2 or later, which incorporates proper bounds checking and input validation for UTF8 sequences in fnmatch operations. System administrators should also implement input sanitization measures at application layers to filter or truncate potentially malicious UTF8 strings before they reach vulnerable library functions. Network segmentation and application whitelisting can reduce attack surface by limiting exposure to potentially vulnerable applications. The vulnerability demonstrates the importance of proper input validation and memory management in system libraries, aligning with ATT&CK technique T1059.007 for command and scripting interpreter usage and T1133 for external remote services. Organizations should also consider implementing runtime monitoring to detect unusual memory allocation patterns that might indicate exploitation attempts. Regular security audits of system libraries and application dependencies remain crucial for identifying similar vulnerabilities in the broader software ecosystem, particularly given the cascading effects such flaws can have across multiple applications and services that depend on core system libraries.