CVE-2018-18505 in Firefox
Summary
by MITRE
An earlier fix for an Inter-process Communication (IPC) vulnerability, CVE-2011-3079, added authentication to communication between IPC endpoints and server parents during IPC process creation. This authentication is insufficient for channels created after the IPC process is started, leading to the authentication not being correctly applied to later channels. This could allow for a sandbox escape through IPC channels due to lack of message validation in the listener process. This vulnerability affects Thunderbird < 60.5, Firefox ESR < 60.5, and Firefox < 65.
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Analysis
by VulDB Data Team • 11/26/2025
This vulnerability represents a critical sandbox escape flaw in Mozilla's browser and email applications that emerged from an incomplete security fix implemented for CVE-2011-3079. The original vulnerability involved insufficient authentication mechanisms in inter-process communication channels, which were partially addressed through the introduction of authentication checks during IPC process creation. However, this remediation contained a significant oversight that allowed for continued exploitation through later-created communication channels. The flaw specifically affects the authentication mechanisms that should validate messages between processes, creating a pathway for malicious actors to bypass security boundaries.
The technical implementation flaw stems from the incomplete application of authentication controls within the IPC subsystem. While the initial fix correctly implemented authentication for channels established during the initial process creation phase, it failed to extend these protections to dynamically created channels that are established after the primary IPC process has been initiated. This creates a window of opportunity where processes can communicate without proper validation, effectively allowing untrusted code to establish connections that should be restricted. The vulnerability operates at the core of Mozilla's security architecture, specifically targeting the listener processes that handle incoming IPC messages and lack proper message validation mechanisms.
From an operational impact perspective, this vulnerability enables sophisticated sandbox escape techniques that can bypass the fundamental security boundaries designed to isolate browser processes from the underlying operating system. Attackers can leverage this flaw to establish unauthorized communication channels between compromised processes and system-level components, potentially enabling privilege escalation or information disclosure. The affected versions include Thunderbird 60.4 and earlier, as well as Firefox ESR 60.4 and earlier, and Firefox 64 and earlier, representing a substantial user base that required immediate attention. This vulnerability aligns with CWE-284 Access Control and CWE-345 Insufficient Verification of Data Authenticity, both of which are critical in process isolation contexts.
The exploitation of this vulnerability follows patterns consistent with the ATT&CK framework's privilege escalation and persistence techniques. Adversaries can utilize this flaw to establish covert communication channels that bypass the intended security boundaries, potentially enabling further attacks such as credential theft or system compromise. The vulnerability's impact is particularly severe because it affects the core security architecture that protects against malicious content execution, making it a high-value target for advanced persistent threat actors. Mitigation efforts should focus on implementing comprehensive authentication validation across all IPC channels, regardless of their creation timing, and ensuring that all message validation occurs at the listener process level to prevent unauthorized communication establishment.
Security organizations should prioritize immediate patch deployment for affected versions, as the vulnerability represents a significant risk to user security. The remediation requires a complete review of the IPC authentication implementation to ensure that all channels receive consistent protection, addressing both the initial channel creation and subsequent dynamic channel establishment. This vulnerability demonstrates the importance of thorough security testing for security fixes, as incomplete implementations can create new attack vectors rather than closing existing ones, highlighting the need for comprehensive regression testing in security patches.