CVE-2007-1352 in Linux
Summary
by MITRE
Integer overflow in the FontFileInitTable function in X.Org libXfont before 20070403 allows remote authenticated users to execute arbitrary code via a long first line in the fonts.dir file, which results in a heap overflow.
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Analysis
by VulDB Data Team • 07/17/2019
The vulnerability identified as CVE-2007-1352 represents a critical integer overflow flaw within the X.Org libXfont library, specifically affecting versions prior to the 20070403 release. This issue manifests in the FontFileInitTable function where improper input validation leads to a heap-based buffer overflow condition. The vulnerability is particularly dangerous because it can be exploited by remotely authenticated users who manipulate the fonts.dir file, a common configuration file used by X Window System applications to manage font resources. The attack vector specifically targets the first line of the fonts.dir file, where an excessively long string can cause integer overflow during memory allocation calculations. This flaw falls under the CWE-190 category of Integer Overflow or Wraparound, which is classified as a fundamental weakness in software design that directly leads to memory corruption vulnerabilities. The technical implementation involves the function incorrectly calculating the required memory allocation size when processing font directory entries, particularly when handling malformed input data that exceeds normal parameter limits.
The operational impact of this vulnerability extends beyond simple code execution, as it creates a pathway for privilege escalation and system compromise within X Window System environments. When an authenticated user successfully crafts a malicious fonts.dir file with an overly long first line, the integer overflow corrupts heap memory structures, potentially allowing attackers to overwrite critical memory locations with malicious code. This heap corruption can lead to arbitrary code execution with the privileges of the affected X server process, which typically runs with elevated permissions to manage graphical interfaces. The vulnerability is particularly concerning in multi-user environments where X server access is granted to untrusted users, as it transforms a simple file manipulation task into a potential system takeover. The exploitation requires minimal privileges since the user must already be authenticated to the system to access font management functionality, but the resulting code execution can be devastating in terms of system integrity and data confidentiality.
Mitigation strategies for CVE-2007-1352 focus primarily on immediate software updates and system hardening measures. The most effective solution involves upgrading to libXfont version 20070403 or later, which includes proper input validation and integer overflow protection mechanisms. System administrators should also implement strict file access controls on font directories and monitor for unauthorized modifications to fonts.dir files. The vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, as it enables attackers to execute arbitrary code and potentially elevate their privileges. Additional defensive measures include implementing application whitelisting policies for font processing applications, enabling heap protection mechanisms such as stack canaries, and conducting regular security audits of X server configurations. Organizations should also consider network segmentation to limit access to X server environments and implement intrusion detection systems to monitor for suspicious font file modifications. The vulnerability demonstrates the importance of proper integer handling in memory management and highlights the need for comprehensive input validation across all system components that process external data, particularly in graphical interface systems where user interaction with configuration files is common.