CVE-2009-2841 in Safari
Summary
by MITRE
The HTMLMediaElement::loadResource function in html/HTMLMediaElement.cpp in WebCore in WebKit before r49480, as used in Apple Safari before 4.0.4 on Mac OS X, does not perform the expected callbacks for HTML 5 media elements that have external URLs for media resources, which allows remote attackers to trigger sub-resource requests to arbitrary web sites via a crafted HTML document, as demonstrated by an HTML e-mail message that uses a media element for X-Confirm-Reading-To functionality, aka rdar problem 7271202.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability described in CVE-2009-2841 represents a significant security flaw in the WebKit rendering engine's handling of HTML5 media elements. This issue affects the HTMLMediaElement::loadResource function within WebCore, which is responsible for managing media resource loading in web browsers. The flaw specifically impacts Apple Safari versions prior to 4.0.4 on Mac OS X, creating a scenario where the browser fails to properly execute expected callbacks when processing external media resources. This technical deficiency stems from the improper handling of media element loading sequences, particularly when dealing with remote URLs that reference external web servers.
The operational impact of this vulnerability is particularly concerning as it enables remote attackers to exploit the browser's media loading mechanism to initiate sub-resource requests to arbitrary websites. The vulnerability can be leveraged through crafted HTML documents, with email messages serving as a primary attack vector. Attackers can construct malicious HTML content that utilizes media elements for X-Confirm-Reading-To functionality, which is a technique commonly used to verify email delivery. This capability allows threat actors to perform covert tracking and reconnaissance activities, as the browser will make requests to specified external domains without user awareness or consent. The vulnerability essentially creates a covert channel that can be used to gather information about user behavior and network activity.
This flaw aligns with CWE-200, which describes improper output neutralization for logs, and relates to broader categories of security issues involving information leakage and unauthorized data transmission. The vulnerability also connects to ATT&CK technique T1566, which covers spearphishing attacks through email, and T1071.004, which involves application layer protocol: DNS, as the malicious requests can be used to exfiltrate information through DNS queries. The attack vector demonstrates how seemingly benign HTML5 media elements can be weaponized to create unauthorized network connections, bypassing typical security controls that monitor for suspicious outbound traffic. The vulnerability essentially undermines the browser's security model by allowing arbitrary external resource loading without proper validation of the requested resources, potentially exposing users to additional threats including cross-site scripting attacks and data exfiltration.
The recommended mitigations for this vulnerability include updating to Safari 4.0.4 or later versions where the issue has been resolved through proper callback implementation in the HTMLMediaElement::loadResource function. System administrators should also implement network monitoring to detect unusual outbound requests from user browsers, particularly those originating from email clients. Additionally, email security solutions should be configured to scan for potentially malicious media element usage in email content, as the vulnerability can be exploited through crafted email messages. Organizations should also consider implementing browser security policies that restrict external resource loading where possible, and deploy network intrusion detection systems that can identify suspicious patterns of external connections initiated through browser media elements. The fix in the updated Safari versions addresses the core issue by ensuring that proper callbacks are executed during media resource loading, thereby preventing the unintended sub-resource requests that were previously possible.