CVE-2023-4575 in Thunderbird
Summary
by MITRE • 09/11/2023
When creating a callback over IPC for showing the File Picker window, multiple of the same callbacks could have been created at a time and eventually all simultaneously destroyed as soon as one of the callbacks finished. This 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
The vulnerability described in CVE-2023-4575 represents a critical use-after-free condition that emerged within the inter-process communication mechanisms of Mozilla Firefox and Thunderbird applications. This flaw specifically manifests when the browser attempts to create a callback for displaying the File Picker window through IPC channels, creating a scenario where multiple identical callback instances can be instantiated simultaneously. The underlying technical issue stems from inadequate synchronization and cleanup mechanisms within the callback management system, where the application fails to properly track and manage the lifecycle of these callback objects during concurrent operations.
The operational impact of this vulnerability extends beyond simple application instability, as it creates a potential exploitation vector for remote code execution attacks. When multiple identical callbacks are created and subsequently destroyed simultaneously upon completion of any single callback, the memory management system experiences a race condition that results in freed memory being accessed by other processes or threads. This use-after-free condition falls under the CWE-416 vulnerability category, which specifically addresses the use of memory after it has been freed, a common pattern in memory corruption vulnerabilities. The flaw is particularly concerning because it occurs within the IPC layer where legitimate browser functionality interacts with system resources, making it an attractive target for attackers seeking to leverage browser-based exploits.
The affected software versions include Firefox versions prior to 117, Firefox ESR versions prior to 102.15 and 115.2, and Thunderbird versions prior to 115.2, indicating this vulnerability has been present in widely deployed browser and email client software. The exploitation of this vulnerability aligns with ATT&CK technique T1059.007, which involves the use of scripting languages for code execution, as attackers could potentially leverage the memory corruption to execute arbitrary code within the browser context. The vulnerability's nature suggests it could be triggered through web content that initiates multiple concurrent file picker operations, potentially through malicious JavaScript or web pages that abuse the IPC callback mechanisms. This makes the vulnerability particularly dangerous in web browsing environments where users may encounter untrusted content, as the exploit could be delivered through standard web traffic without requiring any special privileges or user interaction beyond visiting a malicious website.
The fix for this vulnerability required implementing proper callback lifecycle management and synchronization mechanisms to prevent multiple identical callbacks from being created simultaneously. Security researchers and developers addressed this issue by ensuring that callback instances are properly tracked and destroyed only once, preventing the race condition that led to the use-after-free scenario. Organizations should prioritize immediate patching of affected versions, as this vulnerability represents a significant risk to user security and system integrity. The remediation efforts should include monitoring for any exploitation attempts and ensuring that all systems running affected software versions are updated to the patched releases. Additionally, security teams should implement network monitoring to detect potential exploitation attempts targeting this specific vulnerability, as the use-after-free nature of the flaw makes it particularly suitable for sophisticated exploitation techniques that could bypass standard security measures.