CVE-2010-0520 in Mac OS X
Summary
by MITRE
Heap-based buffer overflow in QuickTimeAuthoring.qtx in QuickTime in Apple Mac OS X before 10.6.3 allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a crafted FLC file, related to crafted DELTA_FLI chunks and untrusted length values in a .fli file, which are not properly handled during decompression.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 05/04/2026
The vulnerability described in CVE-2010-0520 represents a critical heap-based buffer overflow affecting Apple Mac OS X systems running versions prior to 10.6.3. This flaw resides within the QuickTimeAuthoring.qtx component of Apple's QuickTime multimedia framework, specifically during the processing of FLC file format structures. The vulnerability manifests when the system attempts to decompress crafted DELTA_FLI chunks contained within malicious .fli files, creating a dangerous condition where untrusted length values are not properly validated or sanitized before being used in memory allocation operations.
The technical implementation of this vulnerability stems from inadequate input validation within the QuickTime multimedia processing pipeline. When a malicious FLC file containing crafted DELTA_FLI chunks is processed, the system's decompression routine fails to properly validate the length parameters associated with these chunks. This validation failure allows attackers to manipulate memory allocation sizes, leading to heap corruption that can be exploited to overwrite adjacent memory locations. The vulnerability is classified as a heap-based buffer overflow under CWE-122, which specifically addresses buffer overflows occurring in heap memory regions where the buffer size is determined at runtime based on untrusted input data.
The operational impact of this vulnerability extends beyond simple application crashes to encompass full remote code execution capabilities. Attackers can leverage this flaw to execute arbitrary code on vulnerable systems with the privileges of the affected application, typically resulting in complete system compromise. The vulnerability's remote exploitability means that attackers need only deliver a malicious FLC file through standard network channels such as email attachments, web downloads, or file sharing platforms. This creates a significant threat vector as users may unknowingly trigger the vulnerability while opening seemingly legitimate multimedia files, making the attack surface particularly broad and difficult to defend against through user education alone.
The exploitation of this vulnerability aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to initial access and privilege escalation. The attack chain typically begins with delivery of the malicious file through social engineering or compromised websites, followed by execution of the malicious code within the QuickTime processing context. The vulnerability's location within a widely used multimedia framework means that successful exploitation could lead to complete system compromise, as QuickTime processes are typically granted sufficient privileges to access system resources. Organizations should implement multiple layers of defense including timely patch management, network-based intrusion detection systems to identify suspicious file transfers, and user awareness training to recognize potentially malicious file attachments.
Mitigation strategies for CVE-2010-0520 primarily focus on immediate patch deployment and operational security measures. Apple released security updates for Mac OS X 10.6.3 and subsequent versions that properly validate length parameters during FLC file processing, preventing the heap corruption that enables exploitation. System administrators should prioritize patch deployment across all affected systems and implement network segmentation to limit potential lateral movement if exploitation occurs. Additional protective measures include disabling QuickTime processing for untrusted files, implementing file type restrictions for multimedia content, and deploying sandboxing technologies that limit the privileges available to QuickTime processes. The vulnerability's classification as a heap-based buffer overflow also emphasizes the importance of memory safety practices and runtime protections such as stack canaries, address space layout randomization, and data execution prevention mechanisms that can help mitigate exploitation attempts even when patches are not immediately available.