CVE-2025-11719 is a use-after-free vulnerability identified in the native messaging API implementation of Mozilla Firefox and Thunderbird on Windows platforms. The native messaging API allows web extensions to communicate with native applications installed on the host system. Starting from Firefox 143, improper memory management in this API can lead to use-after-free conditions, where memory is accessed after it has been freed, causing memory corruption and application instability. This vulnerability affects all Firefox and Thunderbird versions prior to 144 on Windows. The flaw can be triggered when a malicious or compromised web extension interacts with the native messaging API, potentially causing the browser or email client to crash. Although no exploits have been observed in the wild, the memory corruption could be leveraged by attackers to execute arbitrary code with the privileges of the user running the application. The vulnerability does not require user authentication but does require the presence of a malicious or compromised extension that uses native messaging. The lack of a CVSS score indicates that the vulnerability is newly published and pending further analysis. The root cause lies in the lifecycle management of native messaging connections and associated memory buffers, which are not properly freed or referenced, leading to use-after-free scenarios. This vulnerability underscores the risks associated with native messaging APIs that bridge browser extensions and local system processes, especially on Windows where memory management errors can be exploited for code execution.

For European organizations, this vulnerability poses a risk of browser or email client crashes, leading to potential denial of service and disruption of business operations. More critically, if exploited, it could allow attackers to execute arbitrary code on affected systems, compromising confidentiality, integrity, and availability of sensitive data. Organizations relying heavily on Firefox and Thunderbird on Windows endpoints are at increased risk, especially if they permit installation of third-party or unvetted extensions. The impact extends to sectors with high dependency on secure communications and web browsing, such as finance, government, and critical infrastructure. The lack of known exploits currently reduces immediate risk, but the potential for future exploitation necessitates proactive mitigation. Additionally, exploitation could facilitate lateral movement within networks if attackers gain code execution capabilities on user machines. The vulnerability's exploitation complexity is moderate, requiring a malicious extension or compromise of an existing extension, but no user authentication is needed, increasing the attack surface. Overall, the threat could lead to significant operational and security impacts if left unaddressed.

European organizations should immediately inventory Firefox and Thunderbird deployments on Windows endpoints to identify affected versions prior to 144. They should enforce policies restricting installation of untrusted or unnecessary web extensions, especially those utilizing native messaging. Once Mozilla releases patches for version 144 or later, organizations must prioritize timely updates to eliminate the vulnerability. Employ endpoint detection and response (EDR) solutions to monitor for abnormal crashes or suspicious extension behavior related to native messaging. Network segmentation and application whitelisting can limit the impact of potential exploitation by restricting extension capabilities and native messaging targets. Security teams should audit existing extensions for native messaging usage and remove or update those that are unmaintained or potentially vulnerable. User awareness campaigns should highlight risks of installing extensions from untrusted sources. Finally, organizations should monitor Mozilla security advisories and threat intelligence feeds for updates on exploitation attempts or additional mitigations.