CVE-2023-4573 in Thunderbird
Summary
by MITRE • 09/11/2023
When receiving rendering data over IPC `mStream` could have been destroyed when initialized, which could have led to a use-after-free causing a potentially exploitable crash. This vulnerability affects Firefox < 117, Firefox ESR < 102.15, Firefox ESR < 115.2, and Thunderbird < 115.2.
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Analysis
by VulDB Data Team • 06/20/2025
This vulnerability represents a critical use-after-free condition that emerged within Firefox's inter-process communication framework, specifically affecting the mStream object during rendering data processing. The flaw occurs when the mStream object is destroyed while still being initialized, creating a scenario where subsequent operations attempt to access memory that has already been freed. This type of vulnerability falls under the CWE-416 category, which specifically addresses use-after-free conditions that represent one of the most prevalent and dangerous classes of memory corruption vulnerabilities. The vulnerability impacts multiple Mozilla products including Firefox versions prior to 117, Firefox ESR versions prior to 102.15 and 115.2, and Thunderbird versions prior to 115.2, demonstrating the widespread nature of the issue across the Mozilla ecosystem.
The technical exploitation of this vulnerability leverages the inherent race condition between object initialization and destruction processes within the IPC rendering pipeline. When the mStream object undergoes destruction during its initialization phase, it creates a window where memory management operations can be disrupted, potentially allowing attackers to manipulate the freed memory location for malicious purposes. This scenario aligns with the ATT&CK technique T1059.007, which involves the use of system services and APIs to execute malicious code, particularly through manipulation of memory structures. The vulnerability's exploitable nature stems from the fact that the freed memory could be reallocated and controlled by an attacker, enabling potential code execution or system compromise.
The operational impact of this vulnerability extends beyond simple crash conditions to potentially enable remote code execution in the context of the affected applications. When exploited successfully, the use-after-free condition could allow attackers to execute arbitrary code with the privileges of the affected application, potentially leading to full system compromise. This risk is particularly elevated in browser environments where user interaction is required for exploitation, as the vulnerability could be leveraged through malicious web content. The vulnerability's presence in multiple product lines including Firefox ESR releases indicates that organizations maintaining long-term support versions are also at risk, requiring immediate attention and patching strategies. Security researchers have identified this as a high-severity issue due to its potential for remote exploitation and the critical nature of the rendering subsystem that handles user-facing content.
Mitigation strategies for this vulnerability should prioritize immediate patch deployment across all affected versions of Firefox, Thunderbird, and their respective ESR releases. Organizations should implement network segmentation and monitoring to detect potential exploitation attempts, particularly focusing on unusual memory access patterns or process behavior anomalies. The patch addresses the underlying race condition in the mStream object lifecycle management, ensuring proper synchronization between initialization and destruction operations. Security teams should also consider implementing additional protective measures such as address space layout randomization and heap hardening techniques to further reduce the exploitability of similar vulnerabilities. Regular security assessments and vulnerability scanning should be conducted to identify any related issues in the broader application architecture that might present similar memory management risks.