CVE-2025-11719 is a critical security vulnerability identified in Mozilla Firefox and Thunderbird before version 144, specifically impacting Windows platforms. The issue arises from the native messaging API used by web extensions, which can trigger a use-after-free memory corruption condition. Use-after-free (CWE-416) vulnerabilities occur when a program continues to use memory after it has been freed, leading to undefined behavior such as crashes or arbitrary code execution. In this case, malicious or compromised web extensions leveraging the native messaging API can cause Firefox or Thunderbird to crash or potentially execute arbitrary code with the privileges of the user running the application. The vulnerability does not require any privileges or user interaction to exploit, making it highly dangerous. The CVSS v3.1 base score of 9.8 reflects the critical nature, with attack vector being network-based, low attack complexity, no privileges required, no user interaction needed, and full impact on confidentiality, integrity, and availability. While no known exploits have been reported in the wild yet, the vulnerability’s characteristics suggest it could be weaponized quickly. The native messaging API is commonly used to enable communication between extensions and native applications, so extensions that use this feature are potential attack vectors. The flaw affects all Firefox and Thunderbird versions prior to 144 on Windows, though exact affected versions are unspecified. The vulnerability was publicly disclosed on October 14, 2025, with Mozilla assigned as the vendor and the issue tracked under CWE-416. No official patches or updates are linked yet, indicating the need for immediate attention once available.

The vulnerability poses a significant risk to European organizations using Firefox or Thunderbird on Windows, especially those relying on web extensions that utilize the native messaging API. Exploitation can lead to remote code execution, allowing attackers to gain control over affected systems, steal sensitive data, or disrupt operations by causing application crashes. This threatens confidentiality, integrity, and availability of information systems. Organizations in sectors such as finance, government, healthcare, and critical infrastructure, which often use these applications for communication and browsing, face elevated risks. The lack of required privileges or user interaction lowers the barrier for attackers, increasing the likelihood of exploitation. Additionally, the widespread use of Firefox and Thunderbird in Europe means a large attack surface. The potential for lateral movement within networks following compromise could amplify damage. Given the critical severity and ease of exploitation, failure to address this vulnerability promptly could result in data breaches, operational downtime, and reputational damage.

1. Immediately monitor Mozilla’s official channels for patches addressing CVE-2025-11719 and apply updates to Firefox and Thunderbird version 144 or later as soon as they become available. 2. Temporarily disable or restrict web extensions that use the native messaging API, especially those from untrusted sources, until patches are applied. 3. Implement application whitelisting and restrict installation of unauthorized extensions to reduce attack surface. 4. Employ endpoint detection and response (EDR) solutions capable of detecting memory corruption and anomalous process behavior related to Firefox and Thunderbird. 5. Conduct regular audits of installed extensions and remove any that are unnecessary or suspicious. 6. Educate users about the risks of installing unverified extensions and encourage adherence to security policies. 7. Use network segmentation and least privilege principles to limit potential lateral movement if exploitation occurs. 8. Monitor security advisories and threat intelligence feeds for any emerging exploit activity related to this vulnerability.