CVE-2026-2799 is a use-after-free vulnerability located in the Document Object Model (DOM) Core and HTML components of Mozilla Firefox, affecting all versions prior to 148. Use-after-free 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 or denial of service. In this case, the flaw resides in the handling of DOM elements, which are critical for rendering and interacting with web content. An attacker can craft malicious web pages or content that, when loaded by a vulnerable Firefox browser, trigger the use-after-free condition, potentially allowing execution of arbitrary code in the context of the browser process. This can lead to compromise of user data, browser integrity, and system stability. No public exploits have been reported yet, and no official patches or CVSS scores have been published at the time of disclosure. The vulnerability was reserved and published in February 2026, indicating recent discovery. Given Firefox’s widespread use across desktops and some mobile platforms, the vulnerability has a broad attack surface. The lack of authentication requirements and the ability to trigger the flaw remotely via web content increase the risk. However, exploitation may require precise conditions or user interaction such as visiting a malicious website. The absence of known exploits suggests the vulnerability is not yet actively weaponized but should be addressed promptly. The vulnerability highlights the ongoing risks associated with complex memory management in browser engines and the importance of timely patching and defense-in-depth strategies.

The potential impact of CVE-2026-2799 is significant for organizations and individual users worldwide. Successful exploitation could allow attackers to execute arbitrary code within the context of the Firefox browser, potentially leading to full system compromise depending on the underlying operating system and privilege levels. This threatens confidentiality by exposing sensitive user data, including credentials and browsing history. Integrity could be compromised through manipulation of browser behavior or injected malicious scripts. Availability may be affected if exploitation causes browser crashes or system instability. Organizations relying on Firefox for daily operations, especially those handling sensitive information or operating in high-risk environments, face increased risk of targeted attacks or widespread exploitation once public exploits emerge. The vulnerability also poses risks to critical infrastructure and government entities that use Firefox as a trusted browser. The lack of current exploits provides a window for proactive mitigation, but the broad user base and remote attack vector underscore the urgency of addressing the issue.

Organizations and users should immediately prepare to update Firefox to version 148 or later once patches are released. Until then, practical mitigations include disabling or restricting JavaScript execution in untrusted contexts using browser settings or extensions, as the vulnerability is triggered via crafted web content. Employing browser sandboxing and running Firefox with least privilege can limit the impact of potential exploitation. Network-level protections such as web filtering to block access to suspicious or untrusted websites can reduce exposure. Security teams should monitor threat intelligence feeds for any emerging exploit attempts related to CVE-2026-2799. Additionally, applying strict Content Security Policies (CSP) on internal web applications can help mitigate exploitation risks. Users should avoid visiting unknown or untrusted websites and be cautious with links received via email or messaging platforms. Regular backups and endpoint protection solutions with behavioral detection can help detect and recover from exploitation attempts. Finally, organizations should review and update incident response plans to include scenarios involving browser-based memory corruption vulnerabilities.