CVE-2015-4503 in Firefox
Summary
by MITRE
The TCP Socket API implementation in Mozilla Firefox before 41.0 mishandles array boundaries that were established with a navigator.mozTCPSocket.open method call and send method calls, which allows remote TCP servers to obtain sensitive information from process memory by reading packet data, as demonstrated by availability of this API in a Firefox OS application.
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Analysis
by VulDB Data Team • 06/18/2022
The vulnerability described in CVE-2015-4503 represents a critical memory safety issue within the TCP Socket API implementation of Mozilla Firefox versions prior to 41.0. This flaw specifically affects the handling of array boundaries when establishing TCP connections through the navigator.mozTCPSocket.open method and subsequent send operations. The vulnerability exists in the Firefox OS application environment where the TCP Socket API is exposed to web applications, creating a potential attack surface that could be exploited by remote adversaries.
The technical flaw stems from improper boundary checking within the array management system of the TCP Socket API implementation. When developers use the navigator.mozTCPSocket.open method to establish a connection and subsequently employ send method calls to transmit data, the underlying code fails to properly validate array boundaries before accessing memory locations. This boundary violation occurs during the packet data processing phase where the system attempts to read and transmit information from process memory. The flaw allows attackers to craft specially crafted TCP server responses that can trigger memory access patterns which expose sensitive data from adjacent memory regions.
The operational impact of this vulnerability extends beyond simple information disclosure, as it represents a classic buffer overread condition that can be exploited to extract process memory contents. Attackers can leverage this vulnerability to obtain sensitive information such as cryptographic keys, user credentials, session tokens, or other confidential data stored in memory. The attack vector is particularly concerning in Firefox OS environments where applications have direct access to the TCP Socket API, as it enables remote exploitation without requiring local privileges or complex attack chains. This vulnerability directly aligns with CWE-129, which describes improper validation of array index bounds, and can be categorized under ATT&CK technique T1059.007 for execution through application layer protocols.
The memory exposure occurs because the TCP Socket API implementation does not properly enforce bounds checking when processing incoming packet data. When a remote TCP server sends malformed or specially crafted data packets, the API's array handling code can access memory locations beyond the intended buffer boundaries. This allows attackers to read arbitrary memory contents, potentially including sensitive information from other processes or system components. The vulnerability is particularly dangerous because it operates at the application level within the Firefox OS ecosystem, where the TCP Socket API is designed to provide network connectivity for web applications.
Mitigation strategies for this vulnerability primarily focus on immediate version updates to Firefox 41.0 or later, which contain the necessary patches to correct the array boundary handling in the TCP Socket API implementation. Organizations should also implement network segmentation and monitoring to detect anomalous TCP traffic patterns that might indicate exploitation attempts. Additionally, developers should avoid using the navigator.mozTCPSocket API in applications where memory exposure could lead to significant security implications, and instead utilize more secure networking APIs that properly validate all array boundaries. The fix implemented in Firefox 41.0 addresses the root cause by introducing proper boundary checking mechanisms and ensuring that array access operations validate memory limits before execution, thereby preventing unauthorized memory reads that could expose sensitive process information.