CVE-2015-3724 in iOS
Summary
by MITRE
CoreGraphics in Apple iOS before 8.4 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted ICC profile in a PDF document, a different vulnerability than CVE-2015-3723.
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Analysis
by VulDB Data Team • 07/02/2017
The vulnerability identified as CVE-2015-3724 represents a critical memory corruption flaw within Apple iOS's CoreGraphics framework affecting versions prior to 8.4. This issue specifically manifests when processing ICC color profile data embedded within PDF documents, creating a remote code execution vector that adversaries can leverage from distant locations. The vulnerability operates through a sophisticated attack chain where maliciously crafted ICC profiles are embedded in PDF files, which when opened by vulnerable iOS devices trigger memory corruption conditions. The flaw resides in how CoreGraphics handles color profile parsing operations, particularly when encountering malformed ICC data structures that exceed expected memory boundaries. This type of vulnerability falls under the CWE-125 weakness category, which describes out-of-bounds read conditions that can lead to memory corruption and arbitrary code execution. The attack surface extends beyond simple document viewing to include any application or system component that processes PDF files through the CoreGraphics framework, making it particularly dangerous in enterprise environments where PDF documents are frequently exchanged. The vulnerability is classified under the ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries leverage application vulnerabilities to execute malicious code on target systems.
The technical implementation of this vulnerability exploits memory management weaknesses within CoreGraphics' ICC profile processing routines. When an iOS device encounters a PDF document containing a specially crafted ICC profile, the parsing logic fails to properly validate the profile structure, leading to buffer overflows or heap corruption conditions. The memory corruption occurs during the color space transformation operations where CoreGraphics attempts to map color values between different color profiles. Attackers can construct ICC profiles that contain oversized data structures or malformed header information that causes the parsing engine to write beyond allocated memory boundaries. This memory corruption can be exploited to overwrite critical program structures, function pointers, or return addresses within the execution context, enabling remote code execution with the privileges of the affected application. The vulnerability demonstrates a classic heap-based buffer overflow pattern where the attacker controls the size and content of the data being processed, allowing for precise memory manipulation. The exploitation process requires careful crafting of the ICC profile to ensure that the memory corruption translates into executable code control rather than simple denial of service.
The operational impact of CVE-2015-3724 extends far beyond individual device compromise, affecting enterprise security postures and organizational risk profiles across multiple sectors. Organizations relying on iOS devices for business operations face significant exposure when documents containing malicious ICC profiles are processed through standard PDF readers or email clients. The remote nature of the attack means that adversaries can target users without requiring physical access or local network presence, making it particularly challenging to defend against through traditional network security measures. Mobile device management solutions become critical in mitigating this vulnerability, as they can enforce firmware updates and implement additional security controls around PDF processing. The vulnerability affects not only end-user devices but also enterprise applications that integrate PDF processing capabilities, including document management systems, email servers, and content delivery platforms. Security professionals must consider the broader implications of this vulnerability when conducting risk assessments, as it represents a persistent threat vector that can be exploited through various communication channels including email attachments, web downloads, and document sharing platforms. The exploitability factor of this vulnerability makes it particularly attractive to threat actors seeking to establish persistent access within target organizations.
Mitigation strategies for CVE-2015-3724 must address both immediate remediation and long-term security architecture improvements to prevent exploitation attempts. The primary and most effective mitigation involves updating affected iOS devices to version 8.4 or later, which includes patches that correct the memory handling issues in CoreGraphics. Security administrators should implement comprehensive patch management programs that prioritize iOS updates, particularly for devices handling sensitive information or critical business functions. Network security controls such as PDF content filtering and email attachment scanning can provide additional layers of defense, though these measures are not foolproof given the remote nature of the attack vector. Mobile device management platforms should be configured to disable or restrict PDF processing capabilities where possible, particularly for devices that do not require full PDF functionality. Security monitoring should include detection of suspicious PDF processing activities and anomalous memory usage patterns that could indicate exploitation attempts. Organizations should also consider implementing application whitelisting policies that restrict which applications can process PDF documents, reducing the attack surface for this particular vulnerability. The remediation process requires careful testing of patches to ensure compatibility with existing enterprise applications and workflows, as well as comprehensive user education about the risks of opening untrusted PDF documents containing embedded color profiles. Regular security assessments should verify that all iOS devices within the organization have been successfully updated and that appropriate security controls are in place to prevent exploitation attempts.