CVE-2016-1859 in Safari
Summary
by MITRE
The WebKit Canvas implementation in Apple iOS before 9.3.2, Safari before 9.1.1, and tvOS before 9.2.1 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted web site.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/21/2022
The vulnerability identified as CVE-2016-1859 represents a critical memory corruption flaw within the WebKit rendering engine's canvas implementation across multiple Apple platforms. This weakness affects iOS versions prior to 9.3.2, Safari versions before 9.1.1, and tvOS versions before 9.2.1, creating a widespread attack surface that could be exploited by remote threat actors. The vulnerability stems from improper handling of canvas elements during web page rendering, specifically when processing maliciously crafted web content that triggers buffer overflows or memory corruption conditions. The flaw operates at the intersection of web standards compliance and memory safety, where the canvas API implementation fails to properly validate input parameters and rendering contexts, creating opportunities for attackers to manipulate memory layout and execute arbitrary code. This issue demonstrates a classic buffer overflow vulnerability pattern that has been documented in CWE-121 as a common weakness in memory management, where insufficient bounds checking leads to memory corruption.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a malicious website that leverages specific canvas rendering operations to trigger memory corruption conditions. The attack vector typically involves manipulating canvas element properties, particularly those related to image data manipulation, transformations, and rendering contexts that interact with underlying memory structures. When the affected WebKit implementation processes these crafted canvas operations, it fails to properly validate array bounds or memory allocation parameters, leading to memory corruption that can be leveraged for code execution. The vulnerability's impact extends beyond simple denial of service to full system compromise, as memory corruption can be exploited through return-oriented programming or other advanced exploitation techniques. The flaw operates at the system level within the browser's rendering pipeline, making it particularly dangerous as it can be triggered through standard web browsing activities without requiring any special privileges or user interaction beyond visiting the malicious site.
The operational impact of CVE-2016-1859 is severe given the widespread adoption of affected Apple platforms and the potential for remote code execution. Organizations and individual users operating vulnerable versions of iOS, Safari, or tvOS face significant risk of compromise, as the vulnerability can be exploited through standard web browsing without any user interaction. The memory corruption nature of the flaw means that successful exploitation could lead to complete system compromise, allowing attackers to execute arbitrary code with the privileges of the affected browser process. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under the T1059 category for command and scripting interpreter, as well as T1068 for exploit for privilege escalation. The attack surface includes not only individual users but also enterprise environments where mobile device management policies may not have been updated to address this specific vulnerability, creating potential entry points for advanced persistent threats.
Mitigation strategies for CVE-2016-1859 focus primarily on immediate patching and system updates to the affected Apple platforms. Organizations should prioritize updating all affected iOS devices, Safari installations, and tvOS systems to versions containing the necessary security patches. The remediation process involves applying official security updates from Apple, which address the underlying memory corruption issues in the WebKit canvas implementation. Additionally, network-level mitigations such as web content filtering and sandboxing measures can provide additional protection while waiting for full patch deployment. Security monitoring should focus on detecting attempts to access known malicious websites that leverage this vulnerability, particularly those containing crafted canvas elements designed to trigger memory corruption. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates how seemingly benign web technologies can become attack vectors when implementation flaws exist in core rendering engines. Organizations should also implement security awareness training to educate users about the risks of visiting untrusted websites and the importance of keeping software updated to protect against known vulnerabilities.