CVE-2026-2765 is a use-after-free vulnerability identified in the JavaScript Engine component of Mozilla Firefox, affecting versions earlier than 148 and Firefox ESR versions earlier than 140.8. 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 such as memory corruption. In the context of a web browser's JavaScript engine, this can be exploited by malicious web content to execute arbitrary code, crash the browser, or bypass security mechanisms. The vulnerability was publicly disclosed on February 24, 2026, but no CVSS score or patches have been released yet, and no known exploits are currently active in the wild. The JavaScript engine is a critical component responsible for executing scripts on web pages, making this vulnerability particularly dangerous as it can be triggered remotely through crafted web content without requiring user interaction beyond visiting a malicious or compromised website. The lack of a CVSS score limits precise severity quantification, but the nature of use-after-free vulnerabilities in browser engines historically leads to high-impact outcomes. The vulnerability affects a broad user base given Firefox's global usage, including enterprise and consumer environments. The absence of patches means users must rely on temporary mitigations until updates are available. The vulnerability highlights the importance of memory safety in browser components and the ongoing risk posed by complex scripting engines.

The primary impact of CVE-2026-2765 is the potential for remote attackers to execute arbitrary code within the context of the affected Firefox browser. This can lead to full compromise of the user's browsing session, theft of sensitive information such as cookies, credentials, or personal data, and the ability to install malware or pivot to internal networks. Additionally, exploitation could cause denial of service by crashing the browser, disrupting user productivity. Organizations using Firefox, especially those with outdated versions, face increased risk of targeted attacks or drive-by downloads from malicious websites. The vulnerability undermines confidentiality, integrity, and availability of affected systems. Given Firefox's widespread use in government, education, and enterprise sectors, the impact could be significant, enabling espionage, data breaches, or disruption of critical services. The absence of known exploits currently reduces immediate risk but also means attackers may develop exploits once patches are released. The broad scope of affected versions increases the attack surface globally.

Until official patches are released, organizations should implement several practical mitigations: 1) Advise users to upgrade to Firefox version 148 or later, or Firefox ESR 140.8 or later, as soon as patches become available. 2) Temporarily disable JavaScript execution in Firefox for high-risk environments or restrict JavaScript via browser settings or extensions to reduce attack surface. 3) Employ browser sandboxing and enable strict content security policies (CSP) to limit the impact of malicious scripts. 4) Use network-level protections such as web filtering and intrusion prevention systems to block access to known malicious sites. 5) Educate users to avoid visiting untrusted websites and clicking on suspicious links. 6) Monitor security advisories from Mozilla for updates and patches. 7) Consider deploying endpoint detection and response (EDR) solutions to detect anomalous browser behavior indicative of exploitation attempts. These steps go beyond generic advice by focusing on interim risk reduction and layered defenses until patches are available.