CVE-2004-0478 in Mozilla
Summary
by MITRE
Unknown versions of Mozilla allow remote attackers to cause a denial of service (high CPU/RAM consumption) using Javascript with an infinite loop that continues to add input to a form, possibly as the result of inserting control characters, as demonstrated using an embedded ctrl-U.
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Analysis
by VulDB Data Team • 01/31/2018
This vulnerability affects legacy versions of the Mozilla browser family and represents a classic denial of service flaw that exploits JavaScript execution patterns to consume excessive system resources. The vulnerability occurs when malicious JavaScript code executes an infinite loop that continuously adds input to web forms, leading to uncontrolled resource consumption that can render the browser or system unusable. The specific exploitation technique involves embedding control characters such as ctrl-U to manipulate form input behavior, creating a persistent loop that consumes CPU cycles and memory resources without termination.
The technical root cause lies in the browser's JavaScript engine failing to implement proper loop detection or resource limiting mechanisms during form processing operations. When JavaScript code enters an infinite loop that repeatedly manipulates form elements, the browser's rendering engine and JavaScript interpreter continue executing without bounds, causing progressive resource exhaustion. This type of vulnerability falls under the CWE-835 category of infinite loops or infinite recursion, where the lack of proper loop termination conditions leads to system resource depletion. The vulnerability demonstrates how seemingly benign form manipulation operations can become weaponized when combined with infinite loop constructs and control character injection.
The operational impact of this vulnerability extends beyond simple browser instability to potentially compromise entire system performance and availability. When exploited successfully, the malicious JavaScript causes sustained high CPU utilization and memory consumption, which can affect not only the targeted browser instance but also the underlying operating system's resource management. Attackers can leverage this vulnerability to perform resource exhaustion attacks against users, potentially causing system slowdowns, application crashes, or complete system unresponsiveness. This vulnerability aligns with ATT&CK technique T1496 which describes resource exhaustion attacks targeting system performance through malicious code execution.
Mitigation strategies for this vulnerability require multiple layers of defense including browser updates to patched versions that implement JavaScript execution timeouts and loop detection mechanisms, browser security policies that limit script execution time, and user education about avoiding untrusted content. Modern browser implementations have addressed such issues through enhanced JavaScript engine security features including maximum execution time limits, memory usage monitoring, and automatic script termination when resource thresholds are exceeded. Additionally, implementing content security policies and sandboxing mechanisms can prevent malicious scripts from accessing form elements in ways that could trigger resource exhaustion conditions, providing defense in depth against similar vulnerabilities in the browser ecosystem.