CVE-2021-47784 in Web Browser
Summary
by MITRE • 01/15/2026
Cyberfox Web Browser 52.9.1 contains a denial of service vulnerability that allows attackers to crash the application by overflowing the search bar with excessive data. Attackers can generate a 9,000,000 byte payload and paste it into the search bar to trigger an application crash.
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Analysis
by VulDB Data Team • 01/15/2026
The vulnerability identified as CVE-2021-47784 represents a denial of service flaw within the Cyberfox web browser version 52.9.1 that stems from inadequate input validation in the search bar functionality. This weakness allows malicious actors to deliberately crash the browser application by submitting an extraordinarily large payload of 9,000,000 bytes directly into the search interface. The vulnerability operates through a buffer overflow condition where the application fails to properly handle or limit the size of data entered into the search field, leading to memory corruption and subsequent application termination. Such a flaw demonstrates a fundamental lack of proper bounds checking and input sanitization mechanisms within the browser's user interface components.
From a technical perspective, this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-787, which addresses out-of-bounds write operations. The attack vector specifically targets the browser's search functionality where user input is processed without adequate size limitations or memory allocation controls. When the excessive payload is pasted into the search bar, the browser's internal processing mechanisms attempt to handle the massive amount of data, causing memory allocation failures and ultimately leading to a segmentation fault or similar crash condition. The vulnerability exploits the browser's failure to implement proper input validation and resource management controls during user interaction with the search interface.
The operational impact of this vulnerability extends beyond simple application disruption as it provides attackers with a reliable method for causing service availability issues within the targeted browser environment. This denial of service condition can be executed repeatedly without requiring elevated privileges or specialized knowledge, making it particularly dangerous in environments where browser stability is critical. The vulnerability affects any user who interacts with the search bar functionality, potentially impacting legitimate users during normal browsing operations or providing attackers with a means to disrupt normal business processes. In enterprise environments, this could lead to productivity losses and increased support overhead as users encounter unexpected application crashes.
Mitigation strategies for CVE-2021-47784 should focus on immediate remediation through software updates and patches provided by the vendor. Organizations should implement input validation measures at the application level to prevent excessively large payloads from being processed through the search functionality. Network-level protections could include filtering mechanisms that detect and block unusually large data submissions to browser interfaces. Additionally, implementing browser hardening techniques such as address space layout randomization and stack canaries can help reduce the effectiveness of potential exploitation attempts. Security monitoring should include detection of unusual search bar activity patterns that might indicate attempted exploitation. The vulnerability also highlights the importance of regular security assessments and input validation testing to identify similar weaknesses in other browser components and web applications. Organizations should consider implementing user education programs to raise awareness about potentially malicious input patterns and encourage reporting of unusual browser behavior that might indicate exploitation attempts.