CVE-2016-5270 in Firefox
Summary
by MITRE
Heap-based buffer overflow in the nsCaseTransformTextRunFactory::TransformString function in Mozilla Firefox before 49.0 and Firefox ESR 45.x before 45.4 allows remote attackers to cause a denial of service (boolean out-of-bounds write) or possibly have unspecified other impact via Unicode characters that are mishandled during text conversion.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability CVE-2016-5270 represents a heap-based buffer overflow in Mozilla Firefox's text processing capabilities, specifically within the nsCaseTransformTextRunFactory::TransformString function. This flaw exists in versions prior to Firefox 49.0 and Firefox ESR 45.x before 45.4, making it a significant security concern for users running affected software versions. The issue stems from improper handling of Unicode characters during text conversion processes, which creates a condition where attackers can manipulate memory allocation and write operations beyond intended boundaries.
The technical implementation of this vulnerability involves a boolean out-of-bounds write operation that occurs when the TransformString function processes Unicode characters. This function is responsible for text transformation operations in Firefox's rendering engine, particularly handling case conversion and text formatting. When malformed or specially crafted Unicode sequences are processed, the function fails to properly validate input boundaries, leading to memory corruption that can manifest as heap overflow conditions. The vulnerability is classified under CWE-121 as a heap-based buffer overflow, which is a common class of memory safety issues that can lead to arbitrary code execution or system instability.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable more severe security consequences. Remote attackers can exploit this flaw by crafting malicious web content that triggers the vulnerable text processing path when users visit compromised websites. The out-of-bounds write can corrupt adjacent memory locations, potentially leading to application crashes, browser instability, or in more sophisticated attack scenarios, arbitrary code execution. This vulnerability affects the core rendering engine of Firefox, meaning that successful exploitation could compromise the entire browser session and potentially the underlying operating system, particularly when combined with other exploitation techniques.
Mitigation strategies for CVE-2016-5270 primarily focus on immediate software updates and patches provided by Mozilla. Users should upgrade to Firefox version 49.0 or later, or Firefox ESR 45.4 or later to eliminate the vulnerability. System administrators should prioritize patch deployment across enterprise environments, as this vulnerability can be exploited through web-based attacks without user interaction. Additional protective measures include implementing web application firewalls, enabling content security policies, and utilizing browser security features such as sandboxing and strict MIME type checking. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and code injection through memory corruption, highlighting the need for comprehensive defensive measures including process isolation and memory protection mechanisms. The vulnerability underscores the importance of regular security updates and proper input validation in web browser implementations, particularly for Unicode handling functions that are critical to text rendering and user interface operations.