CVE-2014-0209 in libXfont
Summary
by MITRE
Multiple integer overflows in the (1) FontFileAddEntry and (2) lexAlias functions in X.Org libXfont before 1.4.8 and 1.4.9x before 1.4.99.901 might allow local users to gain privileges by adding a directory with a large fonts.dir or fonts.alias file to the font path, which triggers a heap-based buffer overflow, related to metadata.
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Analysis
by VulDB Data Team • 06/19/2021
The vulnerability identified as CVE-2014-0209 represents a critical security flaw within the X.Org libXfont library affecting versions prior to 1.4.8 and 1.4.9x before 1.4.99.901. This issue stems from integer overflows occurring in two distinct functions: FontFileAddEntry and lexAlias. The flaw enables local attackers to escalate privileges through a carefully crafted manipulation of font directory metadata files, specifically targeting the fonts.dir and fonts.alias files that form part of the X Window System font management infrastructure. The vulnerability exploits the fundamental handling of font metadata within the X11 font subsystem, creating a pathway for privilege escalation attacks that could potentially compromise the entire graphical environment.
The technical implementation of this vulnerability involves the manipulation of integer values during the processing of font directory entries, where the integer overflow conditions lead to heap-based buffer overflows. When a local user adds a directory containing a large fonts.dir or fonts.alias file to the font path, the FontFileAddEntry and lexAlias functions fail to properly validate the size parameters of the font metadata structures. This failure results in the allocation of insufficient memory buffers, causing subsequent writes to overflow into adjacent memory regions. The overflow conditions specifically occur in the context of font file parsing where integer variables representing file sizes or entry counts are not properly checked against maximum allowable values, leading to the classic integer overflow scenario that has been catalogued under CWE-190 as "Integer Overflow or Wraparound."
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise within the X Window System environment. Attackers can leverage this flaw to execute arbitrary code with elevated privileges, potentially gaining root access to the system. The attack vector requires local system access but does not need network connectivity, making it particularly dangerous in multi-user environments where users might have access to font path manipulation capabilities. The vulnerability affects systems running X.Org servers and applications that rely on libXfont for font handling, including desktop environments, window managers, and graphical applications. The exploitation process involves crafting malicious font metadata files that trigger the integer overflow conditions during font path processing, which can occur automatically when the X server loads font directories or when applications access font information through the X11 font subsystem.
Security mitigations for CVE-2014-0209 primarily focus on updating to patched versions of the X.Org libXfont library, specifically versions 1.4.8 and 1.4.99.901 or later. System administrators should implement immediate patch management procedures to ensure all affected systems receive the necessary security updates. Additionally, restricting font path modifications to trusted users and implementing proper input validation for font metadata files can serve as temporary compensating controls. The vulnerability demonstrates the importance of proper integer overflow protection in systems handling user-supplied data, particularly in font processing libraries that are critical to graphical user interfaces. Organizations should also consider implementing monitoring for unusual font path modifications and privilege escalation attempts within their X11 environments. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques using software vulnerabilities and can be categorized under T1068 for Exploitation for Privilege Escalation, with potential lateral movement implications if the compromised system serves as a graphical interface for other networked systems. The vulnerability highlights the need for robust input validation and memory safety practices in font processing code, particularly in widely deployed X11 components that handle untrusted user input through font metadata files.