CVE-2019-9802 in Firefox
Summary
by MITRE
If a Sandbox content process is compromised, it can initiate an FTP download which will then use a child process to render the downloaded data. The downloaded data can then be passed to the Chrome process with an arbitrary file length supplied by an attacker, bypassing sandbox protections and allow for a potential memory read of adjacent data from the privileged Chrome process, which may include sensitive data. This vulnerability affects Firefox < 66.
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Analysis
by VulDB Data Team • 09/07/2023
This vulnerability represents a critical sandbox escape mechanism that exploits the interaction between browser sandboxing and file processing components. The flaw exists in Firefox versions prior to 66 where a compromised sandboxed content process can initiate an FTP download operation that subsequently employs a child process to render the downloaded content. The vulnerability stems from insufficient validation of file length parameters during the data rendering process, allowing an attacker to manipulate the system's memory access patterns. This represents a sophisticated attack vector that leverages the trust relationship between different browser processes while bypassing fundamental security boundaries.
The technical implementation of this vulnerability involves a multi-stage attack chain that begins with compromise of a sandboxed content process and progresses through process spawning and memory manipulation. When the compromised process initiates the FTP download, the child rendering process accepts arbitrary file length parameters that are not properly validated against the memory boundaries of the privileged Chrome process. This allows the attacker to control how much data is read from adjacent memory locations, potentially accessing sensitive information that should remain protected by the sandboxing mechanism. The vulnerability specifically targets the memory management protocols within Firefox's architecture where file length parameters are processed without adequate boundary checking, creating a direct pathway for information disclosure.
The operational impact of this vulnerability extends beyond simple information disclosure to represent a complete bypass of browser sandbox protections. Attackers can leverage this flaw to extract sensitive data from memory locations that should be protected, including but not limited to user credentials, session tokens, and other confidential information. The vulnerability demonstrates a fundamental weakness in Firefox's process isolation mechanisms, where the boundary between unprivileged and privileged processes can be crossed through carefully crafted file length parameters. This creates a persistent threat that can be exploited by remote attackers without requiring additional privileges or local system access, making it particularly dangerous in web browsing environments.
Mitigation strategies for this vulnerability require immediate patching of affected Firefox versions to 66 or later, where the underlying memory handling mechanisms have been corrected. Organizations should implement comprehensive monitoring for suspicious FTP download activities and process spawning patterns that might indicate exploitation attempts. The fix addresses the core issue by implementing proper validation of file length parameters and strengthening the memory access controls between different process levels. This vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and maps to attack techniques in the ATT&CK framework under process injection and privilege escalation categories. Security teams should also consider implementing additional network-level controls to monitor and restrict FTP access where possible, as this vulnerability specifically exploits FTP download capabilities to establish the initial attack vector.