CVE-2025-14321 in Firefox
Summary
by MITRE • 12/09/2025
Use-after-free in the WebRTC: Signaling component. This vulnerability affects Firefox < 146, Firefox ESR < 140.6, Thunderbird < 146, and Thunderbird < 140.6.
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Analysis
by VulDB Data Team • 01/06/2026
The vulnerability identified as CVE-2025-14321 represents a critical use-after-free flaw within the WebRTC signaling component of Mozilla's browser applications. This security issue impacts Firefox versions prior to 146 and Firefox ESR versions prior to 140.6, along with corresponding vulnerable versions of Thunderbird email client. The WebRTC signaling component serves as a crucial communication channel for establishing and managing real-time multimedia sessions between browsers and servers, making it a prime target for exploitation in modern web applications. The flaw manifests when the application fails to properly manage memory references, allowing attackers to potentially execute arbitrary code through crafted web content that triggers the vulnerable code path.
The technical nature of this vulnerability falls under the CWE-416 category of use-after-free conditions, where memory that has been freed is accessed again by the application. In the context of WebRTC signaling, this occurs during the processing of incoming signaling messages that establish peer-to-peer connections. When a malicious actor crafts specially designed WebRTC signaling data, the application may attempt to access memory locations that have already been deallocated, leading to potential memory corruption. This memory corruption can be exploited to overwrite critical program data or execute malicious code with the privileges of the affected application. The vulnerability is particularly concerning because WebRTC is widely deployed in modern web applications, including video conferencing platforms, instant messaging services, and collaborative tools that rely on real-time communication protocols.
The operational impact of CVE-2025-14321 extends beyond simple browser exploitation, as it can enable sophisticated attack vectors within the context of the attacker's broader campaign. According to ATT&CK framework, this vulnerability maps to T1059.007 for command and scripting interpreter and T1566.001 for spearphishing attachment, as attackers can leverage the flaw to deliver malicious payloads through compromised web pages or email attachments. The vulnerability can be exploited through various attack vectors including drive-by downloads, compromised websites, or malicious web applications that utilize WebRTC functionality. Once successfully exploited, the vulnerability allows attackers to execute arbitrary code on the target system, potentially leading to complete system compromise, data exfiltration, or establishment of persistent backdoors. The impact is amplified by the widespread adoption of WebRTC in modern web applications, making the attack surface particularly large.
Mitigation strategies for CVE-2025-14321 should prioritize immediate patching of affected software versions, as this represents the most effective defense against exploitation. Organizations should ensure that Firefox and Thunderbird installations are updated to versions 146 or later for Firefox and 140.6 or later for Firefox ESR and Thunderbird respectively. System administrators should implement network-based protections such as web application firewalls and content filtering solutions that can detect and block malicious WebRTC signaling traffic. Additionally, browser hardening measures including disabling WebRTC when not required, implementing strict content security policies, and using sandboxing technologies can provide additional layers of protection. Security monitoring should include detection of unusual WebRTC signaling patterns and memory access anomalies that might indicate exploitation attempts. The vulnerability also highlights the importance of maintaining up-to-date security patches and implementing robust software update management processes across enterprise environments to prevent exploitation of similar memory corruption vulnerabilities.