CVE-2023-5174 in Thunderbird
Summary
by MITRE • 10/25/2023
If Windows failed to duplicate a handle during process creation, the sandbox code may have inadvertently freed a pointer twice, resulting in a use-after-free and a potentially exploitable crash. *This bug only affects Firefox on Windows when run in non-standard configurations (such as using `runas`). Other operating systems are unaffected.* This vulnerability affects Firefox < 118, Firefox ESR < 115.3, and Thunderbird < 115.3.
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Analysis
by VulDB Data Team • 08/16/2025
This vulnerability represents a critical use-after-free condition that emerged during Windows process creation operations within Firefox's sandbox implementation. The flaw occurs specifically when the Windows operating system fails to duplicate a handle during process creation, creating a scenario where sandbox code inadvertently attempts to free the same memory pointer twice. This double-free condition creates a memory corruption vulnerability that could potentially be exploited by malicious actors to execute arbitrary code within the context of the affected browser application. The vulnerability is particularly concerning because it leverages the underlying Windows handle duplication mechanism to create an exploitable state.
The technical implementation of this vulnerability stems from Firefox's sandboxing architecture which operates differently on Windows compared to other operating systems. When Firefox attempts to create new processes on Windows, it relies on Windows API functions to duplicate handles for security isolation purposes. However, in certain failure scenarios where handle duplication fails, the sandbox code path does not properly account for the error condition, leading to the erroneous double-free operation. This pattern aligns with common software security issues classified under CWE-415, which addresses double free vulnerabilities, and CWE-416, which covers use-after-free conditions. The vulnerability specifically affects Firefox's Windows-specific sandbox implementation and does not manifest on other operating systems due to different process creation and handle management mechanisms.
The operational impact of this vulnerability is significant for users running Firefox in non-standard configurations, particularly those utilizing the `runas` command to execute Firefox with elevated privileges or different user contexts. This creates a potential attack surface where malicious actors could exploit the double-free condition to gain arbitrary code execution within the browser's sandboxed environment. The vulnerability affects multiple product versions including Firefox versions prior to 118, Firefox ESR versions prior to 115.3, and Thunderbird versions prior to 115.3, indicating that the flaw has existed across several release channels and represents a persistent issue in the codebase. Attackers could potentially leverage this vulnerability through crafted web content or malicious downloads that trigger the specific failure path during process creation. The ATT&CK framework would categorize this as a privilege escalation technique under T1068, where an attacker exploits a flaw in software to gain elevated privileges or execute code in a higher privilege context.
Mitigation strategies for this vulnerability primarily involve immediate upgrades to patched versions of Firefox, Firefox ESR, and Thunderbird as recommended by Mozilla security advisories. Users should also avoid running Firefox in non-standard configurations that could trigger the specific failure path, particularly those involving elevated privileges or unusual user contexts. System administrators should monitor for any exploitation attempts and consider implementing additional security controls such as application whitelisting to prevent unauthorized code execution. The underlying issue requires code-level fixes in Firefox's Windows sandbox implementation to properly handle handle duplication failures and prevent the double-free condition from occurring. Organizations should also consider deploying intrusion detection systems that can identify potential exploitation attempts targeting this specific vulnerability pattern. Regular security updates and patch management processes are essential to prevent exploitation of this and similar memory corruption vulnerabilities in browser applications.