CVE-2009-0157 in Mac OS X
Summary
by MITRE
Heap-based buffer overflow in CFNetwork in Apple Mac OS X 10.5 before 10.5.7 allows remote web servers to execute arbitrary code or cause a denial of service (application crash) via long HTTP headers.
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Analysis
by VulDB Data Team • 09/04/2019
The vulnerability identified as CVE-2009-0157 represents a critical heap-based buffer overflow within Apple's CFNetwork framework, which operates as a core networking library in Mac OS X 10.5 versions prior to 10.5.7. This flaw exists in the handling of HTTP headers received from remote web servers, creating a pathway for malicious actors to exploit the system through carefully crafted network traffic. The vulnerability stems from insufficient bounds checking during the processing of HTTP header data, allowing attackers to overflow memory buffers allocated on the heap. The affected CFNetwork component serves as a fundamental building block for network communications across the operating system, making this vulnerability particularly dangerous as it can be triggered by routine web browsing activities.
The technical implementation of this vulnerability involves the improper handling of HTTP header fields that exceed expected length parameters during the parsing process. When CFNetwork receives HTTP headers from a remote server, it allocates memory on the heap to store this data without adequate validation of header length constraints. An attacker can craft HTTP responses containing excessively long header values that surpass the allocated buffer boundaries, causing memory corruption that can be leveraged to execute arbitrary code or force application crashes. This type of heap overflow represents a classic software security flaw that has been documented under CWE-121, which specifically addresses heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The vulnerability's classification aligns with ATT&CK technique T1203, which covers legitimate programs being used for code execution through manipulation of input data.
The operational impact of CVE-2009-0157 extends beyond simple denial of service scenarios to encompass full system compromise capabilities. Remote web servers can exploit this vulnerability to execute malicious code with the privileges of the affected application, potentially leading to complete system compromise. The vulnerability affects all applications that rely on CFNetwork for HTTP communication, which includes the majority of web browsers and network-dependent software on Mac OS X 10.5 systems. This creates a widespread attack surface where a single malicious website can potentially compromise multiple applications and services. The vulnerability's exploitation can result in various outcomes including privilege escalation, data exfiltration, persistent backdoor installation, and complete system takeover. Additionally, the nature of heap corruption makes exploitation particularly challenging to predict and defend against, as the memory layout can vary between system configurations and execution contexts.
Mitigation strategies for this vulnerability primarily focus on applying the official security patches released by Apple, specifically upgrading to Mac OS X 10.5.7 or later versions. System administrators should prioritize immediate patch deployment across all affected systems, as the vulnerability remains exploitable in unpatched environments. Network-level defenses can include implementing HTTP header length restrictions at perimeter devices such as firewalls and proxies, though these measures provide only partial protection as the vulnerability can be triggered through various network protocols and application interfaces. Application developers should consider implementing additional input validation measures within their own applications to provide defense-in-depth protection, particularly for HTTP parsing components. Security monitoring should focus on detecting unusual HTTP traffic patterns and potential exploitation attempts, with particular attention to header length anomalies. The vulnerability serves as a reminder of the critical importance of regular security updates and proper input validation practices, aligning with industry best practices outlined in the OWASP Top Ten and NIST cybersecurity guidelines for buffer overflow prevention and memory safety. Organizations should also implement network segmentation and access controls to limit the potential impact of successful exploitation attempts, as the vulnerability can be leveraged to establish persistent access to compromised systems.