CVE-2025-13020 is a use-after-free vulnerability identified in the WebRTC audio/video component of Mozilla Firefox and Thunderbird. Use-after-free (CWE-416) vulnerabilities occur when a program continues to use a pointer after the memory it points to has been freed, leading to undefined behavior including potential arbitrary code execution. This specific flaw affects Firefox versions earlier than 145 and ESR versions earlier than 140.5, as well as Thunderbird versions earlier than 145 and ESR versions earlier than 140.5. The vulnerability can be triggered remotely by an attacker who crafts malicious WebRTC content and convinces a user to interact with it, such as visiting a malicious website or receiving a malicious message. Exploitation does not require any privileges or prior authentication but does require user interaction, such as opening a webpage or message containing the exploit. Successful exploitation could allow an attacker to execute arbitrary code with the privileges of the user running the browser or email client, leading to full compromise of the affected system. The CVSS v3.1 base score of 8.8 reflects the high impact on confidentiality, integrity, and availability, combined with the ease of remote exploitation and lack of required privileges. No public exploits or active exploitation have been reported at the time of publication, but the vulnerability is considered critical due to the widespread use of Firefox and Thunderbird in both personal and enterprise environments. The lack of available patches at the time of reporting necessitates immediate attention to mitigation strategies to reduce risk.

For European organizations, this vulnerability poses a significant risk due to the widespread use of Firefox and Thunderbird for web browsing and email communications, including in government, finance, healthcare, and critical infrastructure sectors. Exploitation could lead to unauthorized access to sensitive data, system compromise, lateral movement within networks, and disruption of services. The ability to execute arbitrary code remotely without authentication means attackers could deploy malware, ransomware, or espionage tools. Confidentiality breaches could expose personal data protected under GDPR, leading to regulatory penalties and reputational damage. Integrity and availability impacts could disrupt business operations, causing financial losses and undermining trust. Organizations relying heavily on WebRTC for real-time communications may be particularly vulnerable. The absence of known exploits currently provides a window for proactive mitigation, but the high severity score underscores the urgency of addressing this vulnerability to prevent future attacks.

1. Apply patches immediately once Mozilla releases updates addressing CVE-2025-13020 for Firefox and Thunderbird. Monitor Mozilla security advisories closely. 2. Temporarily disable WebRTC functionality in Firefox and Thunderbird if patching is not immediately possible, using configuration settings or extensions that block or restrict WebRTC. 3. Implement network-level controls such as firewall rules or intrusion prevention systems to detect and block suspicious WebRTC traffic patterns. 4. Educate users about the risks of interacting with untrusted web content or email attachments, emphasizing caution with links and media in emails and websites. 5. Employ endpoint detection and response (EDR) tools to monitor for anomalous behavior indicative of exploitation attempts. 6. Restrict browser and email client privileges using sandboxing and application control policies to limit the impact of potential exploitation. 7. Regularly audit and update software inventories to ensure all affected versions are identified and remediated. 8. Coordinate with incident response teams to prepare for potential exploitation scenarios and establish rapid response protocols.