CVE-2021-23965 in Firefox
Summary
by MITRE • 02/26/2021
Mozilla developers reported memory safety bugs present in Firefox 84. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 85.
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Analysis
by VulDB Data Team • 03/05/2021
Mozilla Firefox version 84 contained multiple memory safety vulnerabilities that could potentially lead to arbitrary code execution, as identified in CVE-2021-23965. These memory safety bugs represent critical flaws in the browser's memory management systems that could be exploited by attackers to gain unauthorized control over affected systems. The vulnerability affects Firefox versions prior to 85 and demonstrates the ongoing challenges in maintaining memory safety in complex browser environments where millions of lines of code interact with various memory allocation mechanisms.
The technical nature of these memory safety bugs involves fundamental issues within Firefox's memory management subsystem that could result in memory corruption during normal browser operations. Such corruption typically occurs when programs write beyond allocated memory boundaries or access freed memory locations, creating opportunities for attackers to manipulate program execution flow. These vulnerabilities align with common CWE categories including CWE-121, heap-based buffer overflow, and CWE-122, stack-based buffer overflow, which are frequently exploited in browser-based attacks. The presence of memory corruption evidence suggests that these flaws could be leveraged through sophisticated exploitation techniques that manipulate memory layout to achieve code execution.
The operational impact of CVE-2021-23965 extends beyond simple browser compromise, as successful exploitation could enable attackers to execute arbitrary code with the privileges of the affected Firefox process. This capability provides threat actors with potential access to sensitive user data, browser sessions, and system resources. The vulnerability's exploitation potential aligns with ATT&CK framework techniques including T1059.007 for command and scripting interpreter and T1566 for spearphishing with a malicious attachment, as attackers could craft malicious web content to trigger these memory corruption issues. The attack surface is particularly concerning given that Firefox is widely used and these vulnerabilities could be exploited through standard web browsing activities without requiring special privileges or user interaction beyond visiting malicious websites.
Organizations should prioritize immediate patching of Firefox installations to version 85 or later to mitigate the risk associated with CVE-2021-23965. System administrators should implement comprehensive monitoring for suspicious network traffic patterns that might indicate exploitation attempts, particularly focusing on web-based attacks targeting memory corruption vulnerabilities. Security teams should also consider implementing browser hardening measures including sandboxing, content security policies, and regular security updates as part of their defense-in-depth strategy. The vulnerability underscores the importance of maintaining current security patches and highlights the critical need for continuous security assessment of browser environments, as memory safety issues remain among the most prevalent and dangerous classes of vulnerabilities in modern software applications.