CVE-2007-0647 in Mac OS X
Summary
by MITRE
Format string vulnerability in Help Viewer 3.0.0 allows remote user-assisted attackers to cause a denial of service (crash) via format string specifiers in a filename, which is not properly handled when calling the NSBeginAlertSheet Apple AppKit function.
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Analysis
by VulDB Data Team • 03/09/2025
The vulnerability identified as CVE-2007-0647 represents a critical format string flaw within the Help Viewer 3.0.0 component of Apple's operating system ecosystem. This issue stems from improper input validation and handling of user-supplied data within the NSBeginAlertSheet function of the Apple AppKit framework, which serves as a fundamental component for graphical user interface elements in macOS applications. The flaw specifically manifests when the Help Viewer processes filenames that contain format string specifiers such as %s, %d, or other printf-style formatting characters, creating a scenario where maliciously crafted filenames can trigger unexpected behavior in the application's memory management and execution flow.
The technical exploitation of this vulnerability occurs through a remote user-assisted attack vector where an attacker can craft a specially formatted filename that contains format string specifiers. When the Help Viewer attempts to process this filename, the NSBeginAlertSheet function fails to properly sanitize or escape these format specifiers, leading to a buffer overflow condition or stack corruption. This mismanagement of format strings causes the application to interpret the specifiers as actual formatting instructions rather than literal characters, resulting in unpredictable memory access patterns that ultimately lead to application termination. The vulnerability is classified under CWE-134, which specifically addresses format string vulnerabilities where format strings are constructed from user-controlled data without proper validation or sanitization.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a fundamental security flaw that could potentially be leveraged for more sophisticated attacks if combined with other vulnerabilities. When the Help Viewer crashes due to this format string handling issue, it can cause temporary system instability and disrupt user workflows, particularly in environments where help documentation and system assistance tools are frequently accessed. The vulnerability affects the broader Apple AppKit framework and demonstrates the importance of proper input validation in GUI components that handle user-provided data. From an attacker's perspective, this flaw provides a reliable method for causing application-level disruptions that can be used to deny service to legitimate users while potentially masking more serious underlying security issues.
Mitigation strategies for this vulnerability require immediate patching of the Help Viewer component through official Apple security updates, as well as implementing input validation measures that prevent format string specifiers from being processed as literal filenames. Organizations should also consider implementing network-level controls that restrict access to potentially malicious file downloads and ensure that all system components are kept current with the latest security patches. The vulnerability highlights the importance of following secure coding practices such as those outlined in the OWASP Secure Coding Practices and aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through application-level disruptions. System administrators should monitor for any signs of exploitation attempts and maintain comprehensive logging of Help Viewer access patterns to detect potential abuse of this vulnerability.