CVE-2016-1961 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the nsHTMLDocument::SetBody function in dom/html/nsHTMLDocument.cpp in Mozilla Firefox before 45.0 and Firefox ESR 38.x before 38.7 allows remote attackers to execute arbitrary code by leveraging mishandling of a root element, aka ZDI-CAN-3574.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability identified as CVE-2016-1961 represents a critical use-after-free flaw within the Mozilla Firefox browser's HTML document handling mechanism. This issue resides in the nsHTMLDocument::SetBody function located in dom/html/nsHTMLDocument.cpp, specifically affecting Firefox versions prior to 45.0 and Firefox ESR 38.x versions before 38.7. The vulnerability stems from improper memory management when handling root elements during document processing, creating a scenario where freed memory can be accessed and manipulated by malicious actors. The flaw manifests when the browser encounters specific HTML constructs that trigger the problematic code path, allowing attackers to exploit the memory corruption for code execution.
The technical exploitation of this vulnerability follows a classic use-after-free attack pattern where an attacker crafts malicious HTML content that triggers the vulnerable function path. When Firefox processes this crafted content, the SetBody function improperly handles the root element reference, leading to memory deallocation without proper nullification. Subsequently, when the application attempts to access the freed memory location, it may contain corrupted data or be overwritten with attacker-controlled content. This memory corruption can be leveraged to redirect execution flow, enabling arbitrary code execution with the privileges of the compromised browser process. The vulnerability falls under CWE-416, which specifically addresses use-after-free conditions, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter execution.
The operational impact of CVE-2016-1961 is severe as it provides remote attackers with a straightforward path to achieve arbitrary code execution on vulnerable systems. Attackers can deliver malicious payloads through web pages, making this vulnerability particularly dangerous in the context of browser-based attacks. The exploitability is enhanced by the fact that no user interaction is required beyond visiting a malicious website, making it suitable for drive-by download scenarios. The vulnerability affects a wide range of Firefox installations, including both regular releases and extended support releases, amplifying its potential impact across different user bases. Organizations relying on Firefox for web browsing face significant risk from this vulnerability, as it can be exploited through standard web browsing activities without requiring special privileges or complex attack vectors.
Mitigation strategies for CVE-2016-1961 primarily focus on immediate patching of affected Firefox installations to version 45.0 or later for regular releases and 38.7 for ESR releases. System administrators should prioritize deployment of security updates across all affected browsers in their environments, particularly in enterprise settings where multiple users may be exposed to web-based threats. Additionally, implementing web application firewalls and content filtering solutions can provide an additional layer of protection by blocking known malicious content. Browser hardening measures such as disabling unnecessary browser features, implementing strict content security policies, and using sandboxing technologies can reduce the attack surface and limit potential exploitation. Network monitoring solutions should be configured to detect and alert on suspicious web traffic patterns that may indicate exploitation attempts. Organizations should also consider implementing security awareness training to help users recognize and avoid potentially malicious websites that could exploit this vulnerability.