CVE-2026-2784 is a security vulnerability identified in the Mozilla Firefox web browser, specifically affecting versions earlier than 148 and Firefox ESR versions earlier than 140.8. The vulnerability is categorized as a mitigation bypass within the DOM (Document Object Model) security component. The DOM is a critical part of the browser responsible for managing the structure and content of web pages and enforcing security policies that prevent unauthorized script actions and data access. A mitigation bypass in this context implies that an attacker can circumvent built-in security mechanisms designed to isolate or restrict potentially harmful web content or scripts. Although detailed technical specifics are not provided, such bypasses typically allow malicious web pages or scripts to perform actions that should be blocked, such as accessing sensitive data, executing unauthorized code, or manipulating the browser environment beyond intended constraints. The vulnerability was reserved on February 19, 2026, and published on February 24, 2026, but no CVSS score or patch information is currently available. No known exploits have been reported in the wild, indicating that active exploitation has not yet been observed. However, given Firefox's widespread use across personal, enterprise, and government environments, the vulnerability poses a significant risk. Attackers could leverage this flaw by enticing users to visit crafted malicious websites or by injecting malicious content into legitimate sites. The lack of a CVSS score requires an assessment based on potential impact and exploitability factors. Since the vulnerability affects core browser security controls and could lead to unauthorized data access or code execution, it is considered high severity. The absence of required authentication and the possibility of exploitation through user browsing behavior increase the risk profile. Organizations should prioritize monitoring Mozilla's security advisories for patches and consider interim mitigations to reduce exposure.

The vulnerability in Firefox's DOM security component could have severe consequences for organizations and users worldwide. Exploitation may allow attackers to bypass security mitigations, potentially leading to unauthorized access to sensitive information, session hijacking, or execution of malicious scripts within the browser context. This undermines the confidentiality and integrity of user data and may facilitate further attacks such as credential theft, data exfiltration, or lateral movement within networks. Since Firefox is widely used in corporate, governmental, and personal environments, the scope of impact is broad. Enterprises relying on Firefox for secure web access could face increased risk of data breaches and compliance violations. Additionally, the vulnerability could be leveraged in targeted attacks against high-value individuals or organizations, especially if combined with social engineering tactics. The absence of known exploits currently limits immediate impact, but the potential for rapid weaponization once details become public is significant. The vulnerability also threatens availability indirectly by enabling attacks that disrupt user sessions or browser stability. Overall, the threat compromises core browser security guarantees, making it a critical concern for cybersecurity defenses globally.

Until official patches are released by Mozilla, organizations should implement several specific mitigations to reduce risk. First, restrict access to untrusted or suspicious websites through network-level filtering and web proxy controls to limit exposure to malicious content. Enable and enforce Firefox’s built-in security features such as Enhanced Tracking Protection, strict site isolation, and disabling potentially risky browser extensions. Employ endpoint security solutions with browser exploit mitigation capabilities that can detect and block suspicious script behaviors. Educate users about the risks of visiting unknown or untrusted websites and the importance of prompt browser updates. Monitor Mozilla’s security advisories closely and prepare to deploy updates immediately upon release. For high-security environments, consider temporarily using alternative browsers with unaffected versions or hardened configurations. Additionally, implement network segmentation and data loss prevention controls to limit the impact of any potential compromise originating from browser exploitation. Regularly audit browser configurations and usage policies to ensure compliance with security best practices. These targeted actions go beyond generic advice by focusing on reducing attack surface and enhancing detection until a patch is available.