CVE-2016-1959 in Firefox
Summary
by MITRE
The ServiceWorkerManager class in Mozilla Firefox before 45.0 allows remote attackers to execute arbitrary code or cause a denial of service (out-of-bounds read and memory corruption) via unspecified use of the Clients API.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability identified as CVE-2016-1959 resides within the ServiceWorkerManager class of Mozilla Firefox versions prior to 45.0, representing a critical security flaw that exposes the browser to remote code execution and denial of service attacks. This issue specifically manifests through improper handling of the Clients API, which is part of the service worker specification designed to enable background processing and offline functionality in web applications. The vulnerability stems from inadequate bounds checking and memory management within the browser's service worker implementation, creating a pathway for malicious actors to manipulate memory structures and potentially execute arbitrary code on affected systems. The flaw demonstrates characteristics consistent with memory corruption vulnerabilities that fall under CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write vulnerabilities that can lead to memory corruption.
The technical exploitation of this vulnerability occurs when a malicious web page leverages the Clients API in conjunction with service worker functionality to trigger memory corruption through improper bounds checking. Attackers can craft specially crafted web content that, when loaded in Firefox, causes the ServiceWorkerManager to access memory locations beyond allocated buffers or perform invalid memory operations. This can result in arbitrary code execution with the privileges of the browser process, potentially allowing attackers to install malware, steal user data, or compromise the entire system. The out-of-bounds read conditions can also lead to information disclosure, where attackers might extract sensitive memory contents, and ultimately cause denial of service by crashing the browser process or corrupting critical memory structures.
The operational impact of this vulnerability extends beyond simple exploitation as it affects the core browser functionality and user security posture. Users of affected Firefox versions face significant risk when browsing the web, as the vulnerability can be triggered through seemingly benign web content without user interaction. This makes it particularly dangerous for phishing attacks, drive-by downloads, and other social engineering campaigns where attackers can leverage the vulnerability to gain unauthorized access to systems. The vulnerability also impacts the browser's ability to maintain stable operation, as memory corruption can cause unpredictable behavior and system instability. From an attacker perspective, this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the T1059.007 sub-technique for scripting, where adversaries use browser-based scripting to execute malicious code. The vulnerability's nature also relates to T1190, which covers exploiting vulnerabilities in web applications, making it a prime target for automated exploitation frameworks.
Mitigation strategies for CVE-2016-1959 primarily focus on immediate patching of affected Firefox installations to version 45.0 or later, where the underlying memory management issues have been addressed through improved bounds checking and memory validation mechanisms. Organizations should implement comprehensive browser update policies to ensure all users maintain current versions of Firefox, as the vulnerability affects a wide range of operating systems including Windows, macOS, and Linux platforms. Security researchers and organizations should also consider implementing network-level protections such as web application firewalls and content filtering solutions to detect and block malicious content that might attempt to exploit this vulnerability. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping their browsers updated. The fix implemented by Mozilla addresses the root cause by strengthening memory management within the ServiceWorkerManager class and ensuring proper validation of API parameters before processing client requests, effectively closing the attack vector that allowed for out-of-bounds memory access and subsequent code execution.