CVE-2008-0668 in Gnumeric
Summary
by MITRE
The excel_read_HLINK function in plugins/excel/ms-excel-read.c in Gnome Office Gnumeric before 1.8.1 allows user-assisted remote attackers to execute arbitrary code via a crafted XLS file containing XLS HLINK opcodes, possibly because of an integer signedness error that leads to an integer overflow. NOTE: some of these details are obtained from third party information.
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Analysis
by VulDB Data Team • 08/05/2019
The vulnerability described in CVE-2008-0668 represents a critical code execution flaw within the Gnome Office Gnumeric spreadsheet application, specifically affecting versions prior to 1.8.1. This vulnerability resides in the excel_read_HLINK function located within the plugins/excel/ms-excel-read.c file, which processes Microsoft Excel files for import into the Gnumeric application. The flaw manifests when processing XLS files containing HLINK opcodes, which are used to define hyperlinks within Excel documents. The vulnerability is classified as a user-assisted remote attack vector, meaning that an attacker must convince a user to open a maliciously crafted file, but the actual execution occurs on the victim's system without requiring additional privileges from the attacker.
The technical root cause of this vulnerability stems from an integer signedness error that results in an integer overflow condition within the parsing logic. When Gnumeric processes the HLINK opcodes from the malicious XLS file, the application fails to properly validate or handle the size parameters associated with these opcodes. This improper handling creates a scenario where an attacker can craft an XLS file with specifically manipulated data that causes the integer overflow during the parsing process. The overflow occurs when the application attempts to allocate memory or process data structures based on values that have been manipulated through the signedness error, leading to unpredictable memory behavior that can be exploited to execute arbitrary code.
The operational impact of this vulnerability is severe and potentially devastating for users who rely on Gnumeric for spreadsheet processing. An attacker who successfully exploits this vulnerability can gain complete control over the victim's system, allowing for arbitrary code execution with the privileges of the user running Gnumeric. This could enable attackers to install malware, steal sensitive data, modify files, or establish persistent access to the compromised system. The vulnerability affects all users who process Microsoft Excel files with Gnumeric, particularly those who might receive XLS files from untrusted sources, making it a significant threat in environments where spreadsheet processing is common. The integer overflow condition creates a memory corruption scenario that can be leveraged through various exploitation techniques, including stack smashing and heap-based attacks.
The vulnerability aligns with CWE-190, which describes integer overflow and underflow conditions, and represents a classic example of how improper input validation can lead to memory corruption vulnerabilities. From an attack perspective, this flaw maps to several ATT&CK techniques including initial access through malicious file delivery, execution through code injection, and privilege escalation if the user has elevated permissions. The attack chain typically involves social engineering to convince users to open the malicious XLS file, followed by the exploitation of the integer overflow during file parsing. Mitigation strategies should include immediate patching to Gnumeric version 1.8.1 or later, which contains the necessary fixes for the integer overflow condition. Additionally, users should implement strict file validation policies, avoid opening files from untrusted sources, and maintain updated antivirus signatures that can detect malicious XLS files. Network-level protections such as email filtering and web application firewalls can also help prevent the delivery of malicious files to users, while system hardening measures like disabling automatic file processing and implementing sandboxing can reduce the potential impact of successful exploitation attempts.