CVE-2017-12109 in libxls
Summary
by MITRE
An exploitable integer overflow vulnerability exists in the xls_preparseWorkSheet function of libxls 1.4 when handling a MULRK 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.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 03/07/2023
The vulnerability identified as CVE-2017-12109 represents a critical integer overflow flaw within the libxls library version 1.4, specifically within the xls_preparseWorkSheet function. This issue manifests when processing MULRK records in Microsoft Excel files, creating a pathway for remote code execution through memory corruption. The vulnerability stems from inadequate input validation and arithmetic overflow handling during the parsing of spreadsheet data structures, making it particularly dangerous for applications that process untrusted Excel files.
The technical implementation of this vulnerability involves an integer overflow condition that occurs during the calculation of memory allocation for processing MULRK records. When a maliciously crafted XLS file contains specially formatted data that triggers this overflow, the system allocates insufficient memory space for the parsed data structure. This memory corruption creates opportunities for attackers to manipulate memory layout and potentially execute arbitrary code. The flaw operates at the intersection of buffer management and integer arithmetic, where the overflow results in a write operation beyond allocated memory boundaries, violating fundamental memory safety principles.
From an operational perspective, this vulnerability presents significant risk to organizations relying on libxls for Excel file processing, including document management systems, spreadsheet analysis tools, and automated data processing pipelines. The remote code execution capability means that attackers can compromise systems simply by delivering a malicious XLS file, without requiring any interactive user actions or specific system access. The vulnerability affects systems across multiple operating environments where libxls is integrated, making it particularly widespread in enterprise document processing scenarios. Security professionals must consider this as a high-priority issue given its remote exploitability and potential for system compromise.
The mitigation strategy for CVE-2017-12109 requires immediate patching of libxls library installations to version 1.4.1 or later, which contains the necessary fixes for the integer overflow condition. Organizations should also implement strict file validation procedures, including content scanning and sandboxing of Excel files before processing. Network-based protections such as email filtering and web application firewalls can help prevent delivery of malicious files. Additionally, system hardening measures including stack protection mechanisms and address space layout randomization should be enabled to reduce exploit reliability. The vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and maps to ATT&CK technique T1203, Exploitation for Client Execution, highlighting the need for comprehensive endpoint protection strategies. Regular security audits and vulnerability assessments should be conducted to identify similar issues in other third-party libraries and ensure complete remediation across all affected systems.