CVE-2025-4091 in Thunderbird
Summary
by MITRE • 04/29/2025
Memory safety bugs present in Firefox 137, Thunderbird 137, Firefox ESR 128.9, and Thunderbird 128.9. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Thunderbird < 138, and Thunderbird ESR < 128.10.
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Analysis
by VulDB Data Team • 08/16/2025
The vulnerability identified as CVE-2025-4091 represents a critical memory safety issue affecting multiple Mozilla products including Firefox and Thunderbird across both regular and extended support release versions. This classification aligns with CWE-121 which encompasses memory safety issues such as buffer overflows and memory corruption that can lead to arbitrary code execution. The affected software versions demonstrate the typical risk profile of memory safety vulnerabilities where improper memory management can create exploitable conditions that adversaries might leverage for malicious purposes.
These memory safety bugs manifest as potential memory corruption issues within the browser and email client implementations, indicating flaws in how these applications handle memory allocation and deallocation processes. The presence of evidence suggesting memory corruption directly correlates with the potential for remote code execution attacks, particularly when considering that the vulnerability affects widely used applications that process untrusted data from web content and email messages. Such vulnerabilities are particularly dangerous because they can be triggered through common user activities like visiting compromised websites or opening malicious email attachments.
The operational impact of this vulnerability extends beyond simple functionality degradation to encompass serious security risks for affected users. Attackers could potentially exploit these memory safety issues to execute arbitrary code on vulnerable systems, leading to complete system compromise. This risk is particularly elevated given that Firefox and Thunderbird are widely deployed applications that handle sensitive user data and are frequently targeted by threat actors. The vulnerability affects both regular and extended support releases, indicating that organizations running older versions may be exposed to these risks for extended periods.
Mitigation strategies should prioritize immediate patching of affected versions to address the underlying memory safety issues. Organizations should implement comprehensive vulnerability management programs that include regular updates and security patches across all deployed software versions. The ATT&CK framework categorizes such vulnerabilities under T1059 which covers execution through command and scripting interpreters, highlighting the potential for these memory corruption issues to serve as initial access vectors for more sophisticated attack chains. Additionally, implementing network segmentation and application whitelisting controls can provide defense-in-depth measures to limit the potential impact of exploitation attempts. Security teams should also monitor for indicators of compromise related to these specific vulnerabilities and consider implementing automated threat hunting processes to detect potential exploitation attempts in their environments.