CVE-2016-10585 in libxl
Summary
by MITRE
libxl provides Node bindings for the libxl library for reading and writing excel (XLS and XLSX) spreadsheets. libxl downloads zipped resources over HTTP, which leaves it vulnerable to MITM attacks. It may be possible to cause remote code execution (RCE) by swapping out the requested zip file with an attacker controlled zip file if the attacker is on the network or positioned in between the user and the remote server.
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Analysis
by VulDB Data Team • 02/10/2020
The vulnerability identified as CVE-2016-10585 resides within the libxl library, a Node.js module designed for handling Microsoft Excel spreadsheet formats including both legacy XLS and modern XLSX files. This library facilitates reading and writing operations through its Node.js bindings for the underlying libxl C++ library. The core issue emerges from the library's implementation of resource downloading mechanisms that rely on unencrypted HTTP connections for retrieving zipped spreadsheet components. This design flaw creates a fundamental security weakness that directly violates security best practices for network communication and data integrity protection.
The technical flaw manifests when libxl attempts to download external resources from remote servers using HTTP protocols without implementing any form of cryptographic verification or integrity checking. This vulnerability creates a man-in-the-middle attack surface where malicious actors positioned within the network traffic path can intercept the HTTP requests and substitute the legitimate zip files with attacker-controlled malicious payloads. The specific nature of this vulnerability aligns with CWE-319, which addresses the exposure of sensitive information through improper use of network protocols. The library's failure to implement secure communication channels creates an attack vector that can be exploited to execute arbitrary code on the target system.
The operational impact of this vulnerability extends beyond simple data compromise, as it can potentially lead to full system compromise through remote code execution. When an attacker successfully replaces a legitimate zip file with a malicious one, the consequences can range from data theft and system infiltration to complete system takeover depending on the execution context and privileges available to the Node.js process. This vulnerability particularly affects environments where users may be accessing spreadsheets containing external references or where the library is used in automated processing pipelines that fetch resources from untrusted sources. The risk is amplified in corporate networks or public Wi-Fi environments where network position attacks are more feasible.
Mitigation strategies for this vulnerability should focus on implementing secure communication practices and network security controls. Organizations should immediately upgrade to patched versions of the libxl library where HTTPS support and cryptographic verification have been implemented. Network administrators should consider deploying firewalls or proxy servers that enforce HTTPS traffic for external resource downloads and implement network segmentation to limit exposure. The remediation process should also include reviewing all applications using libxl to ensure proper input validation and resource handling. Additionally, implementing certificate pinning mechanisms and network monitoring to detect suspicious traffic patterns can provide additional layers of defense. This vulnerability demonstrates the critical importance of secure coding practices and the necessity of validating all external resource downloads through authenticated and encrypted channels, aligning with ATT&CK technique T1071.004 for application layer protocol use and T1566 for credential access through network sniffing.