CVE-2015-5773 in Mac OS X
Summary
by MITRE
QL Office in Apple iOS before 8.4.1 and OS X before 10.10.5 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted office document.
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Analysis
by VulDB Data Team • 02/03/2025
The vulnerability identified as CVE-2015-5773 represents a critical memory corruption flaw within QL Office, Apple's Quick Look framework that enables previewing office documents without fully opening them. This vulnerability affects iOS versions prior to 8.4.1 and OS X versions prior to 10.10.5, creating a significant attack surface for remote adversaries who can craft malicious office documents to exploit the underlying memory management issues. The flaw resides in how the Quick Look framework processes office documents, specifically in the handling of memory structures during document parsing operations. The vulnerability manifests through improper bounds checking and memory allocation practices that allow attackers to manipulate memory pointers and execute arbitrary code within the context of the Quick Look process. This represents a classic buffer overflow condition that falls under CWE-121, which describes direct allocation of memory in a buffer that is too small for the data being copied into it, or CWE-122, which describes insufficient space in buffer for data being copied to it. The attack vector leverages the automatic preview functionality that many users rely on when browsing files, making it particularly dangerous as users may inadvertently trigger the exploit simply by viewing a malicious document in a file browser or email client.
The operational impact of CVE-2015-5773 extends beyond simple code execution to include potential denial of service conditions that can crash applications and render systems unstable. When exploited successfully, the vulnerability can cause memory corruption that leads to application crashes, system instability, and in some cases complete system compromise. The remote nature of the attack means that adversaries can deliver malicious documents through various channels including email attachments, web downloads, or file sharing platforms without requiring user interaction beyond the initial preview action. This vulnerability directly maps to several tactics in the MITRE ATT&CK framework including T1059 for command and control, T1068 for exploit for privilege escalation, and T1190 for exploitation of remote services. The memory corruption aspects of this vulnerability also align with ATT&CK technique T1070 for indicator removal and T1133 for external remote services, as attackers may use the executed code to establish persistent access or exfiltrate data from compromised systems.
The technical exploitation of this vulnerability requires attackers to craft specifically formatted office documents that trigger the memory corruption during Quick Look processing. The attack typically involves manipulating document structure elements such as headers, footers, or embedded objects in ways that cause the memory allocation routines to overflow or corrupt adjacent memory regions. The vulnerability is particularly concerning because the Quick Look framework operates with elevated privileges in many contexts, potentially allowing attackers to escalate privileges beyond the initial code execution. System administrators and security professionals should note that this vulnerability affects not only individual user systems but also enterprise environments where automatic document previews are commonly enabled. The impact is amplified in environments where users frequently access email or browse file shares containing potentially malicious documents, making the vulnerability particularly dangerous in corporate or educational settings where document sharing is prevalent. Organizations should implement immediate mitigations including disabling Quick Look previews for office documents, applying the relevant security patches, and monitoring for suspicious file access patterns that may indicate exploitation attempts. The vulnerability also underscores the importance of keeping all system components updated, as the patch for this issue required updating the Quick Look framework and related document processing libraries to properly validate memory operations and prevent the buffer overflow conditions that enabled the exploit.