CVE-2011-1659 in C Library
Summary
by MITRE
Integer overflow in posix/fnmatch.c in the GNU C Library (aka glibc or libc6) 2.13 and earlier allows context-dependent attackers to cause a denial of service (application crash) via a long UTF8 string that is used in an fnmatch call with a crafted pattern argument, a different vulnerability than CVE-2011-1071.
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Analysis
by VulDB Data Team • 12/28/2024
The vulnerability identified as CVE-2011-1659 represents a critical integer overflow flaw within the GNU C Library implementation of the fnmatch function. This issue specifically affects glibc versions 2.13 and earlier, where the library fails to properly validate input lengths when processing UTF8 strings through the fnmatch system call. The vulnerability arises from inadequate bounds checking in the posix/fnmatch.c source file, creating a scenario where maliciously crafted input can trigger unexpected behavior in applications relying on this standard library function.
The technical exploitation of this vulnerability occurs when an attacker provides an excessively long UTF8 string combined with a specially crafted pattern argument to the fnmatch function. The integer overflow manifests during internal calculations that determine string processing boundaries, causing the application to allocate insufficient memory or compute incorrect buffer sizes. This flaw operates within the context of applications that utilize fnmatch for pattern matching operations, particularly those handling user-supplied input or configuration data that may contain UTF8 encoded characters. The vulnerability is classified under CWE-190 as an integer overflow error, specifically involving signed integer overflow conditions that can lead to memory corruption and system instability.
From an operational perspective, this vulnerability presents a significant denial of service risk that can be exploited by context-dependent attackers to crash applications using the affected glibc version. The impact extends beyond simple application termination, as the overflow can potentially lead to more severe consequences including arbitrary code execution if the overflow affects critical memory regions. The vulnerability's exploitation requires specific conditions involving UTF8 string processing and fnmatch calls, making it less trivial to exploit than some other vulnerabilities but still posing a substantial risk to systems running vulnerable glibc versions. Network-based attackers can leverage this flaw to target applications that process user input through fnmatch operations, particularly in web applications, file processing utilities, and system management tools.
Security mitigations for CVE-2011-1659 primarily involve upgrading to patched versions of glibc where the integer overflow has been corrected through proper input validation and bounds checking. System administrators should prioritize updating their glibc installations to versions 2.14 or later, which contain the necessary fixes for this vulnerability. Additionally, organizations should implement input validation measures at application layers to reduce the attack surface, particularly when processing untrusted UTF8 data through fnmatch operations. The vulnerability demonstrates the importance of proper integer handling in system libraries and aligns with ATT&CK technique T1499.004 for denial of service attacks through resource exhaustion. Organizations should also consider implementing monitoring for unusual fnmatch behavior and establish robust patch management procedures to prevent exploitation of similar integer overflow vulnerabilities in other system components.