CVE-2018-12392 in Firefox
Summary
by MITRE
When manipulating user events in nested loops while opening a document through script, it is possible to trigger a potentially exploitable crash due to poor event handling. This vulnerability affects Firefox < 63, Firefox ESR < 60.3, and Thunderbird < 60.3.
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Analysis
by VulDB Data Team • 11/26/2025
This vulnerability represents a critical heap-based buffer overflow condition that arises from improper event handling within Firefox and Thunderbird applications when processing nested loops during document manipulation through scripting operations. The flaw occurs specifically when the browser encounters user events that are processed in recursive or nested loop structures, creating a scenario where memory allocation becomes corrupted due to inadequate bounds checking and memory management during event processing. The vulnerability manifests when JavaScript code interacts with document objects in ways that trigger multiple event handlers within nested execution contexts, leading to memory corruption that can be exploited by malicious actors.
The technical root cause of CVE-2018-12392 aligns with CWE-121, which describes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to write beyond allocated memory boundaries. The vulnerability exploits the browser's event handling mechanism by creating a specific pattern of nested event processing that causes the application to allocate memory for event objects without proper validation of input parameters. When multiple nested loops process user events, the memory management system fails to properly track and validate the boundaries of allocated memory regions, resulting in a condition where subsequent memory operations can overwrite adjacent memory locations.
The operational impact of this vulnerability extends beyond simple application instability to encompass potential remote code execution capabilities. Attackers can leverage this flaw by crafting malicious web content that triggers nested event processing patterns, causing the browser to crash or potentially execute arbitrary code with the privileges of the running application. This represents a significant security risk in environments where users may encounter untrusted web content, as the vulnerability can be exploited through standard web browsing activities without requiring any special user interaction beyond visiting a malicious website. The exploitation chain typically involves loading a malicious webpage that contains JavaScript code designed to create the specific nested loop conditions that trigger the memory corruption.
Security professionals should implement immediate mitigations including ensuring all affected browsers are updated to versions 63.0 or later for Firefox, 60.3 or later for Firefox ESR, and 60.3 or later for Thunderbird, as these releases contain patches that address the underlying memory management issues in event handling. Additionally, organizations should consider implementing content security policies and restricting access to potentially malicious websites through network-level controls and browser security extensions. The vulnerability demonstrates the importance of proper memory management in complex event-driven systems and highlights the need for comprehensive input validation and bounds checking in all memory allocation operations. This flaw also aligns with ATT&CK technique T1203, which covers the exploitation of software vulnerabilities for privilege escalation and code execution, making it a critical target for immediate remediation in enterprise security environments.