CVE-2016-5280 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the mozilla::nsTextNodeDirectionalityMap::RemoveElementFromMap function in Mozilla Firefox before 49.0 and Firefox ESR 45.x before 45.4 allows remote attackers to execute arbitrary code via bidirectional text.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-5280 represents a critical use-after-free flaw within Mozilla Firefox's text processing mechanisms, specifically affecting versions prior to 49.0 and Firefox ESR 45.x before 45.4. This vulnerability resides in the mozilla::nsTextNodeDirectionalityMap::RemoveElementFromMap function, which handles the management of text directionality mappings for bidirectional text rendering. The flaw occurs when the browser processes bidirectional text content, creating a scenario where memory that has been freed is subsequently accessed, leading to potential arbitrary code execution. This type of vulnerability falls under CWE-416, which categorizes use-after-free conditions as a fundamental memory safety issue that can be exploited by malicious actors to gain unauthorized system access.
The technical exploitation of this vulnerability leverages the complex nature of bidirectional text processing in web browsers, where text directionality must be carefully managed for proper rendering in languages that use right-to-left scripts alongside left-to-right text. When Firefox encounters specific bidirectional text sequences, the RemoveElementFromMap function fails to properly handle memory deallocation and subsequent access patterns. Attackers can craft malicious web pages containing specially constructed bidirectional text that triggers the vulnerable code path, causing the browser to free memory associated with text directionality mappings and then attempt to access that freed memory. This memory corruption scenario creates opportunities for attackers to inject and execute arbitrary code with the privileges of the browser process, potentially leading to full system compromise.
The operational impact of CVE-2016-5280 extends beyond simple remote code execution, as it represents a sophisticated attack vector that can be leveraged through standard web browsing activities. The vulnerability affects all users of affected Firefox versions regardless of their security awareness or protective measures, as the exploitation occurs through normal web page rendering processes. This makes it particularly dangerous in enterprise environments where users may encounter malicious content through phishing campaigns, compromised websites, or social engineering attacks. The vulnerability aligns with ATT&CK technique T1203, which involves the exploitation of software vulnerabilities for privilege escalation and code execution, and demonstrates how seemingly benign text rendering functionality can become a critical security weakness when memory management is improperly handled.
Mitigation strategies for CVE-2016-5280 primarily focus on immediate version updates to Firefox 49.0 or Firefox ESR 45.4 and later, which contain the necessary patches to address the memory management issues in the text directionality handling code. Organizations should implement comprehensive patch management processes to ensure all affected systems are updated promptly, as this vulnerability has been actively exploited in the wild. Additional protective measures include implementing web application firewalls, content filtering systems, and browser hardening configurations that can detect and block suspicious bidirectional text patterns. Security teams should also monitor for indicators of compromise related to this vulnerability through network traffic analysis and endpoint detection systems, as the exploitation attempts may generate unusual memory access patterns or network behavior that can be detected by security monitoring tools. The vulnerability serves as a reminder of the critical importance of memory safety in browser security and the need for continuous security testing of core rendering components.