CVE-2009-0744 in Safari
Summary
by MITRE
Apple Safari 4 Beta build 528.16 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a feeds: URI beginning with a (1) % (percent), (2) { (open curly bracket), (3) } (close curly bracket), (4) ^ (caret), (5) ` (backquote), or (6) | (pipe) character, followed by an & (ampersand) character.
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Analysis
by VulDB Data Team • 01/27/2025
The vulnerability identified as CVE-2009-0744 represents a critical denial of service flaw in Apple Safari 4 Beta build 528.16 that stems from improper handling of specially crafted feeds: URIs. This vulnerability operates at the application level and demonstrates a classic null pointer dereference condition that leads to application instability and crashes. The flaw specifically manifests when Safari processes feed URIs that begin with one of six specific special characters followed by an ampersand character, creating a parsing inconsistency that can be exploited remotely by attackers.
The technical implementation of this vulnerability involves the browser's URI parsing mechanism failing to properly validate and sanitize input sequences that begin with percent, open curly bracket, close curly bracket, caret, backquote, or pipe characters followed by ampersands. When Safari encounters such malformed feed URIs, the parsing routine attempts to dereference a null pointer during the processing of these sequences, causing the application to crash and terminate unexpectedly. This behavior aligns with CWE-476, which describes null pointer dereference vulnerabilities, and represents a fundamental flaw in input validation and error handling within the browser's feed processing subsystem.
From an operational perspective, this vulnerability creates significant security implications as it allows remote attackers to execute denial of service attacks against Safari users without requiring any special privileges or authentication. The attack vector is particularly concerning because feed URIs can be embedded in web pages, emails, or other digital content that users might inadvertently click on, making this a widespread potential threat. The vulnerability affects users running Safari 4 Beta build 528.16 and represents a regression in browser security that could be exploited in various attack scenarios including social engineering campaigns or targeted attacks against specific user groups.
The exploitation of this vulnerability follows patterns consistent with the attack technique described in the MITRE ATT&CK framework under T1499, which covers network denial of service attacks. Attackers can craft malicious web content containing these specially formatted feed URIs that, when processed by the vulnerable browser, will trigger the crash condition. The impact extends beyond simple application instability as it can be used to disrupt user productivity, potentially serve as a precursor to more sophisticated attacks, and demonstrate the browser's insufficient input sanitization capabilities. Organizations and users should consider this vulnerability as part of a broader threat landscape where browser-based attacks are increasingly sophisticated and require comprehensive security measures.
Mitigation strategies for this vulnerability should include immediate patching of Safari installations to the latest stable versions that contain the necessary fixes for feed URI parsing. System administrators should implement browser security policies that restrict the processing of external feed content and consider deploying network-level controls that can detect and block suspicious URI patterns. Additionally, user education about the dangers of clicking on untrusted links and the importance of keeping browser software updated should be emphasized. The vulnerability underscores the importance of robust input validation and error handling in web browser implementations and serves as a reminder that even seemingly minor parsing flaws can lead to significant security consequences.