CVE-2007-4568 in X11
Summary
by MITRE
Integer overflow in the build_range function in X.Org X Font Server (xfs) before 1.0.5 allows context-dependent attackers to execute arbitrary code via (1) QueryXBitmaps and (2) QueryXExtents protocol requests with crafted size values, which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 07/27/2019
The vulnerability identified as CVE-2007-4568 represents a critical integer overflow flaw within the X.Org X Font Server xfs component prior to version 1.0.5. This vulnerability resides in the build_range function which processes font-related protocol requests from clients. The flaw manifests when the server handles QueryXBitmaps and QueryXExtents protocol requests that contain crafted size values, creating a condition where integer arithmetic operations exceed the maximum representable value for signed integers. This overflow condition directly leads to heap-based buffer overflow conditions that can be exploited by remote attackers to execute arbitrary code on the affected system. The vulnerability is context-dependent, meaning that exploitation requires specific conditions related to the protocol interactions and the precise manipulation of size parameters in the font query operations.
The technical implementation of this vulnerability stems from inadequate input validation and integer overflow handling within the font server's protocol processing layer. When the build_range function processes client requests containing oversized size parameters, the integer overflow occurs during the calculation of buffer sizes needed for font data processing. This overflow corrupts adjacent memory regions in the heap, potentially allowing attackers to overwrite critical program data structures or function pointers. The heap-based nature of the overflow means that the attacker can manipulate memory layout to achieve code execution, often through return-oriented programming techniques or direct overwrite of execution control flow. The vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions that can lead to buffer overflows and arbitrary code execution.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise when exploited successfully. Attackers can leverage this flaw to gain unauthorized access to systems running vulnerable xfs versions, potentially leading to data breaches, system takeover, or further network infiltration. The remote exploitability of this vulnerability means that attackers do not require physical access to the system, making it particularly dangerous in networked environments where font servers might be exposed to external traffic. Organizations using X.Org X Font Server in production environments face significant risk if they have not updated to version 1.0.5 or later, as the vulnerability can be exploited without authentication and provides a direct path to code execution. This vulnerability also maps to ATT&CK technique T1059.007 for command and control through the use of arbitrary code execution capabilities.
Mitigation strategies for CVE-2007-4568 primarily focus on immediate software updates and system hardening measures. The most effective remediation involves upgrading to X.Org X Font Server version 1.0.5 or later, which contains the necessary patches to address the integer overflow conditions in the build_range function. System administrators should also implement network segmentation to limit access to font servers, disable unnecessary font server services when not required, and deploy intrusion detection systems to monitor for suspicious protocol requests. Additional protective measures include implementing input validation controls, enabling address space layout randomization, and using stack canaries to detect buffer overflow attempts. The vulnerability demonstrates the importance of proper integer overflow handling in server applications and highlights the need for comprehensive security testing of protocol implementations, particularly those involving dynamic memory allocation and user-supplied data processing. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain current vulnerability assessments to identify systems potentially affected by similar issues in other components.