CVE-2001-1489

Step 1: Payload Delivery: The attacker crafts a malicious HTML webpage. This webpage contains a significant number of image tags (<img>) referencing either real images or, more efficiently, small, lightweight images or even empty image placeholders. Step 2: Webpage Loading: The victim user accesses the malicious webpage using Internet Explorer 6. Step 3: Image Parsing and Rendering: Internet Explorer 6 begins to parse the HTML and process the image tags. For each image tag, the browser attempts to load, decode, and render the image. Step 4: Resource Exhaustion: Due to the large number of images, the browser's image rendering engine consumes excessive CPU cycles and memory. The browser struggles to efficiently manage the resources required for each image. Step 5: Denial of Service: The excessive resource consumption leads to a denial-of-service condition. The browser becomes unresponsive, freezes, or crashes, preventing the user from interacting with the webpage or other applications.

The vulnerability stems from a resource exhaustion issue within Internet Explorer 6's image rendering engine. The browser fails to properly manage the allocation and deallocation of memory and CPU cycles when processing a large number of image elements within a single webpage. Specifically, the flaw lies in the inefficient handling of image metadata and the repeated parsing and processing of image data. This leads to a memory leak and excessive CPU utilization, eventually causing the browser to become unresponsive or crash. The root cause is likely an unoptimized algorithm for image handling, coupled with a lack of proper resource limits or garbage collection mechanisms for image data. The browser's inability to efficiently handle a large number of images, combined with the lack of proper resource management, creates a denial-of-service condition.