CVE-2021-23964 in Firefox
Summary
by MITRE • 02/26/2021
Mozilla developers reported memory safety bugs present in Firefox 84 and Firefox ESR 78.6. 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, Thunderbird < 78.7, and Firefox ESR < 78.7.
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Analysis
by VulDB Data Team • 05/04/2025
Mozilla Firefox and Thunderbird versions prior to 85 and 78.7 respectively contain critical memory safety vulnerabilities that could potentially allow remote code execution. These memory safety bugs were identified by Mozilla developers during routine security audits and represent a significant threat to user systems. The vulnerabilities manifest as memory corruption issues that could be exploited by attackers to gain unauthorized control over affected systems. The presence of evidence suggesting memory corruption indicates that these flaws could be leveraged to execute malicious code remotely without user interaction.
The technical nature of these vulnerabilities falls under memory safety issues that are commonly categorized as heap-based buffer overflows, use-after-free conditions, or other memory corruption patterns. Such flaws typically occur when programs fail to properly manage memory allocation and deallocation, allowing attackers to manipulate memory contents and potentially redirect program execution flow. These types of vulnerabilities are particularly dangerous because they can be exploited through various attack vectors including malicious web content, email attachments, or crafted web pages that trigger the vulnerable code paths. The exploitation of such memory corruption flaws often requires sophisticated techniques and may involve multiple steps to achieve successful code execution.
The operational impact of these vulnerabilities extends across multiple Mozilla products including Firefox web browser, Thunderbird email client, and the Firefox Extended Support Release versions. Organizations using affected versions face significant risk of compromise, particularly in environments where users may encounter malicious content through web browsing or email communications. The vulnerability affects not only individual users but also enterprise environments where these applications are widely deployed. The potential for remote code execution means that attackers could install malware, steal sensitive data, or establish persistent access to compromised systems. These vulnerabilities are particularly concerning because they can be exploited without user interaction, making them ideal candidates for automated attacks.
Security practitioners should prioritize immediate patching of all affected versions to prevent exploitation. The recommended mitigation strategy involves updating to Firefox 85, Thunderbird 78.7, or Firefox ESR 78.7 respectively. Organizations should implement comprehensive monitoring to detect potential exploitation attempts and ensure that all systems are updated promptly. The vulnerability aligns with common attack patterns found in the attack framework, particularly those related to memory corruption exploitation and privilege escalation. According to CWE classification, these issues typically map to CWE-119, which covers "Improper Access to Memory Location" and CWE-787, which addresses "Out-of-bounds Write". The attack surface for these vulnerabilities includes web content rendering, email processing, and various application functions that handle untrusted input. Organizations should also consider implementing network segmentation and application whitelisting to limit potential damage from successful exploitation attempts.