CVE-2017-12108 in libxls
Summary
by MITRE
An exploitable integer overflow vulnerability exists in the xls_preparseWorkSheet function of libxls 1.4 when handling a MULBLANK record. A specially crafted XLS file can cause a memory corruption resulting in remote code execution. An attacker can send malicious XLS file to trigger this vulnerability.
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Analysis
by VulDB Data Team • 03/07/2023
The CVE-2017-12108 vulnerability represents a critical integer overflow flaw within the libxls library version 1.4, specifically within the xls_preparseWorkSheet function that processes MULBLANK records. This vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, where an application fails to properly handle integer arithmetic that results in values exceeding the maximum representable value for the data type. The affected library is commonly used for parsing Microsoft Excel files, making it a widespread component across various applications and systems that process xls documents.
The technical exploitation of this vulnerability occurs when a maliciously crafted XLS file contains a MULBLANK record with manipulated data that triggers integer overflow during memory allocation calculations. When the xls_preparseWorkSheet function processes this record, it performs arithmetic operations on user-supplied values without proper bounds checking, leading to an integer overflow condition. This overflow results in incorrect memory allocation sizes being calculated, which subsequently causes memory corruption when the application attempts to write data to the improperly allocated memory regions. The vulnerability is particularly dangerous because it can be triggered through simple file attachment mechanisms, making it suitable for remote code execution attacks.
The operational impact of this vulnerability extends across numerous software applications that depend on libxls for Excel file processing, including office suites, data analysis tools, and enterprise applications. Attackers can leverage this vulnerability by crafting malicious XLS files that, when opened or processed by vulnerable applications, will execute arbitrary code on the target system. The attack vector is particularly concerning because it requires no user interaction beyond opening the file, making it a prime candidate for phishing campaigns and social engineering attacks. This vulnerability is categorized under the ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries exploit vulnerabilities in software to execute code on target systems.
Mitigation strategies for CVE-2017-12108 primarily focus on immediate software updates and patches provided by the libxls maintainers. Organizations should prioritize updating to libxls version 1.4.1 or later, which contains the necessary fixes for this integer overflow condition. Additionally, implementing strict file validation and sanitization measures can help reduce the attack surface by filtering out potentially malicious XLS files before they reach vulnerable applications. Network-level protections such as email filtering and web application firewalls can also help prevent the delivery of malicious files. Security monitoring should include detection of suspicious file processing activities and memory allocation patterns that may indicate exploitation attempts, particularly in environments where Excel files are regularly processed or shared.