CVE-2013-6462 in Secure Global Desktop
Summary
by MITRE
Stack-based buffer overflow in the bdfReadCharacters function in bitmap/bdfread.c in X.Org libXfont 1.1 through 1.4.6 allows remote attackers to cause a denial of service (crash) or possibly execute arbitrary code via a long string in a character name in a BDF font file.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 06/17/2021
The vulnerability identified as CVE-2013-6462 represents a critical stack-based buffer overflow flaw within the X.Org libXfont library version range 1.1 through 1.4.6. This issue specifically affects the bdfReadCharacters function located in the bitmap/bdfread.c source file, which processes BDF (Bitmap Distribution Format) font files commonly used in X Window System implementations. The flaw arises from inadequate input validation when handling character names within BDF font files, creating a condition where maliciously crafted font data can overwrite adjacent stack memory locations. The vulnerability operates under CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue in software development practices. Attackers can exploit this weakness by crafting a BDF font file containing an excessively long string in the character name field, triggering the buffer overflow during font parsing operations.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable remote code execution, making it particularly dangerous in networked environments. When a vulnerable application processes a malicious BDF font file, the stack-based buffer overflow can cause application crashes or, in more sophisticated attack scenarios, allow adversaries to execute arbitrary code with the privileges of the affected process. This represents a significant threat to systems running X Window System implementations, including Linux desktop environments, servers, and embedded systems that utilize X11 for graphical user interfaces. The vulnerability is particularly concerning because BDF font files are commonly used in various graphical applications and can be encountered during normal system operations, making exploitation more likely than in specialized attack scenarios. The attack surface includes any system component that processes BDF font files, including window managers, desktop environments, and applications that render text using X11 libraries.
Mitigation strategies for CVE-2013-6462 should prioritize immediate patching of affected libXfont versions, with the implementation of proper input validation and bounds checking in all font parsing functions. System administrators should implement strict font file validation policies, particularly for user-uploaded or network-retrieved font content, and consider deploying runtime protections such as stack canaries and address space layout randomization to reduce exploit reliability. The vulnerability demonstrates the importance of adhering to secure coding practices and proper memory management in graphics libraries, as highlighted by ATT&CK technique T1059.007 for application execution through font rendering processes. Organizations should also consider implementing network segmentation and access controls to limit exposure of systems to potentially malicious font files, while monitoring for unusual font processing activity that might indicate exploitation attempts. Additionally, regular security audits of X Window System components and comprehensive vulnerability assessments should be conducted to identify similar memory safety issues in related graphics libraries and font processing components.