CVE-2018-5129 in Firefox
Summary
by MITRE
A lack of parameter validation on IPC messages results in a potential out-of-bounds write through malformed IPC messages. This can potentially allow for sandbox escape through memory corruption in the parent process. This vulnerability affects Thunderbird < 52.7, Firefox ESR < 52.7, and Firefox < 59.
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Analysis
by VulDB Data Team • 11/26/2025
This vulnerability represents a critical security flaw in Mozilla's browser and email client software that stems from insufficient input validation within inter-process communication mechanisms. The issue manifests when malformed IPC messages are processed without proper parameter validation, creating an opportunity for attackers to manipulate memory structures through carefully crafted malicious communications between different process boundaries. The vulnerability specifically affects the communication layer that enables sandboxed content processes to interact with the parent browser process, where the absence of proper bounds checking allows for memory corruption that could be exploited to escape the sandbox environment.
The technical implementation of this vulnerability resides in the IPC message handling code where developers failed to validate the parameters of incoming messages before processing them. When these malformed messages are received, the system attempts to write data to memory locations that exceed the allocated buffer boundaries, resulting in an out-of-bounds write condition. This type of memory corruption can potentially be leveraged by attackers to overwrite critical memory structures, function pointers, or other sensitive data within the parent process memory space. The flaw operates at the intersection of process isolation and memory management, where the sandbox protection mechanism that typically isolates untrusted content can be bypassed through strategic memory corruption.
The operational impact of this vulnerability extends beyond simple memory corruption, as it provides a potential pathway for complete system compromise through sandbox escape techniques. Attackers who can successfully exploit this vulnerability gain the ability to execute arbitrary code within the parent process context, effectively breaking out of the restricted sandbox environment that normally protects the browser from malicious content. This escalation allows for access to sensitive user data, system resources, and potentially full system control, making it particularly dangerous in environments where users browse untrusted content or receive malicious emails. The vulnerability affects multiple Mozilla products including Thunderbird and various Firefox versions, indicating a widespread impact across the software ecosystem.
The exploitation of this vulnerability aligns with several tactics described in the attack framework, particularly those involving privilege escalation and sandbox bypass techniques. From a cybersecurity perspective, this issue demonstrates the critical importance of input validation and memory safety in security-critical components such as IPC mechanisms. The vulnerability can be classified under CWE-129 as "Improper Validation of Array Index" and potentially CWE-787 as "Out-of-bounds Write," highlighting the fundamental nature of the flaw in memory management. Mitigation strategies should focus on immediate patch deployment across all affected versions, as well as implementing additional runtime protections such as address space layout randomization and stack canaries. Organizations should also consider network-based protections and monitoring for unusual IPC message patterns that might indicate exploitation attempts, while maintaining regular security updates to prevent similar vulnerabilities from emerging in future releases.