CVE-2009-1709 in Safari
Summary
by MITRE
Use-after-free vulnerability in the garbage-collection implementation in WebCore in WebKit in Apple Safari before 4.0 allows remote attackers to execute arbitrary code or cause a denial of service (heap corruption and application crash) via an SVG animation element, related to SVG set objects, SVG marker elements, the targetElement attribute, and unspecified "caches."
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Analysis
by VulDB Data Team • 09/06/2019
The CVE-2009-1709 vulnerability represents a critical use-after-free flaw within Apple Safari's WebKit rendering engine that fundamentally undermines memory safety mechanisms. This vulnerability resides in the garbage-collection implementation of WebCore, which serves as the core rendering component responsible for processing web content including Scalable Vector Graphics. The flaw specifically manifests when processing SVG animation elements, particularly those involving SVG set objects and marker elements that utilize the targetElement attribute. The vulnerability operates through a sophisticated memory corruption pathway that exploits improper handling of object references during the garbage collection process, creating conditions where freed memory blocks can be accessed and manipulated by malicious actors.
The technical exploitation of this vulnerability leverages the interaction between SVG animation processing and WebKit's memory management system. When Safari encounters certain SVG elements with animation attributes, particularly those involving marker elements and targetElement references, the garbage collector fails to properly track object lifecycles. This creates a scenario where an object reference becomes invalid while still being accessible, allowing attackers to manipulate freed memory locations. The unspecified "caches" mentioned in the vulnerability description suggest that internal caching mechanisms within WebKit's SVG processing pipeline contribute to the instability, potentially storing references to objects that are subsequently freed but still accessed during animation processing. The vulnerability operates under CWE-416, which specifically addresses use-after-free conditions, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage in exploitation contexts.
The operational impact of this vulnerability extends beyond simple denial of service to encompass full remote code execution capabilities, making it particularly dangerous in web browsing environments. Attackers can craft malicious SVG content that, when rendered by Safari, triggers the memory corruption conditions leading to heap corruption and subsequent arbitrary code execution. This vulnerability affects all versions of Safari prior to version 4.0, representing a significant attack surface for malicious actors targeting users of older browser versions. The heap corruption resulting from this flaw can manifest as application crashes, browser instability, or more sinisterly, provide attackers with opportunities to execute malicious payloads with the privileges of the browser process. The vulnerability's remote nature means that simply visiting a compromised website or viewing an embedded SVG element can trigger the exploit, making it particularly dangerous in phishing campaigns and drive-by download scenarios.
Mitigation strategies for CVE-2009-1709 primarily focus on immediate browser updates to version 4.0 or later, where Apple implemented corrected garbage collection mechanisms for WebCore. System administrators should prioritize patching affected Safari installations and consider implementing browser security policies that restrict SVG content processing where possible. Network-level defenses can include content filtering solutions that block suspicious SVG elements or implement strict MIME type validation for web content. Organizations should also consider deploying web application firewalls that can detect and prevent exploitation attempts targeting this specific vulnerability. The fix implemented by Apple addressed the core garbage collection logic and improved memory lifecycle management for SVG elements, specifically targeting the interaction between set objects, marker elements, and the targetElement attribute that previously led to the use-after-free condition. Security monitoring should include detection of anomalous SVG processing patterns and memory allocation behaviors that could indicate exploitation attempts.