CVE-2015-4041 in Coreutils
Summary
by MITRE
The keycompare_mb function in sort.c in sort in GNU Coreutils through 8.23 on 64-bit platforms performs a size calculation without considering the number of bytes occupied by multibyte characters, which allows attackers to cause a denial of service (heap-based buffer overflow and application crash) or possibly have unspecified other impact via long UTF-8 strings.
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Analysis
by VulDB Data Team • 05/19/2022
The vulnerability identified as CVE-2015-4041 resides within the GNU Coreutils library, specifically affecting versions through 8.23 on 64-bit systems. This flaw manifests in the keycompare_mb function located within the sort.c file, which handles multibyte character comparisons during sorting operations. The core issue stems from improper memory management when processing UTF-8 encoded strings, where the function fails to account for the variable byte length characteristics inherent to multibyte character encodings. This oversight creates a fundamental mismatch between the calculated buffer size and the actual memory requirements needed to process the input data correctly.
The technical implementation flaw operates by utilizing a size calculation mechanism that assumes a fixed byte representation for all characters, completely disregarding the fact that UTF-8 characters can occupy 1 to 4 bytes depending on their Unicode value. When attackers provide sufficiently long UTF-8 strings that trigger this miscalculation, the system allocates insufficient memory space for the operation, leading to heap-based buffer overflow conditions. This vulnerability directly maps to CWE-122, which describes insufficient memory allocation for buffers, and represents a classic example of improper handling of variable-length data structures. The buffer overflow occurs at runtime when the application attempts to write beyond the allocated memory boundaries, potentially causing application crashes or more severe system instability.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it creates potential pathways for more sophisticated attacks. While the primary effect manifests as heap-based buffer overflows and application crashes, the underlying memory corruption could theoretically be exploited to achieve arbitrary code execution under certain conditions. Attackers can leverage this vulnerability by crafting specially formatted UTF-8 strings that, when processed through the sort utility, trigger the memory allocation error. The vulnerability affects any system running GNU Coreutils 8.23 or earlier versions where the sort command is executed with multibyte character input, making it particularly relevant in internationalized environments where UTF-8 encoding is prevalent.
Mitigation strategies for CVE-2015-4041 primarily focus on immediate version upgrades to GNU Coreutils 8.24 or later, which contain the necessary patches to properly handle multibyte character size calculations. System administrators should prioritize patching affected systems and verify that all instances of the sort utility are updated across the environment. Additionally, input validation measures can be implemented at the application level to filter or sanitize UTF-8 strings before processing, though this approach provides only partial protection. The vulnerability demonstrates the importance of proper memory management in internationalized applications and aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion. Organizations should also consider implementing monitoring solutions to detect unusual patterns in sort command usage that might indicate exploitation attempts, while maintaining comprehensive system logging to track potential vulnerability exploitation activities.