CVE-2026-2779 is a security vulnerability identified in Mozilla Firefox's Networking: JAR component, specifically caused by incorrect boundary conditions. This flaw affects all Firefox versions prior to 148 and Firefox ESR versions prior to 140.8. The Networking: JAR component handles Java Archive (JAR) files, which are used to package Java classes and associated metadata. Incorrect boundary conditions typically refer to errors in validating or enforcing limits on data buffers or input sizes, which can lead to memory corruption issues such as buffer overflows or underflows. Such memory corruption can be exploited to execute arbitrary code, cause denial of service, or bypass security controls. Although no known exploits have been reported in the wild at the time of publication, the vulnerability's presence in a widely used browser component presents a significant risk. The lack of a CVSS score means the exact severity is not formally quantified, but the nature of the flaw suggests a high potential impact. Mozilla has reserved the CVE and published the vulnerability details on February 24, 2026, but no patch links are currently provided, indicating that fixes may be forthcoming or in progress. The vulnerability requires no user interaction beyond visiting a malicious or compromised site serving crafted JAR files, making exploitation potentially straightforward. Given Firefox's broad user base across consumer, enterprise, and government sectors, the vulnerability could be leveraged in targeted attacks or widespread campaigns once exploit code becomes available.

The potential impact of CVE-2026-2779 is significant due to the widespread use of Mozilla Firefox globally. Exploitation of the incorrect boundary conditions in the Networking: JAR component could lead to memory corruption, enabling attackers to execute arbitrary code within the context of the browser. This could compromise user confidentiality by stealing sensitive data, integrity by manipulating browser behavior or content, and availability by causing crashes or denial of service. Organizations relying on Firefox for secure web access, including government agencies, financial institutions, and enterprises, could face targeted attacks aiming to breach internal networks or exfiltrate data. The absence of known exploits currently limits immediate risk, but the vulnerability's characteristics suggest that once exploit code is developed, rapid weaponization is possible. The impact extends to any system running affected Firefox versions, including desktops, laptops, and potentially embedded systems using Firefox ESR. Failure to patch promptly could expose organizations to advanced persistent threats or opportunistic attackers leveraging this flaw to gain initial access or escalate privileges.

To mitigate CVE-2026-2779, organizations and users should immediately plan to upgrade Mozilla Firefox to version 148 or later, or Firefox ESR to version 140.8 or later once these updates are released. Until patches are available, consider disabling or restricting the use of the Networking: JAR component if feasible, or employ browser security controls such as sandboxing and strict content security policies to limit exposure. Network-level defenses like web proxies and intrusion detection systems should be updated to detect and block suspicious JAR file traffic or malformed network packets targeting this component. Security teams should monitor Mozilla advisories and threat intelligence feeds for updates on exploit development and patch releases. Additionally, educating users to avoid untrusted websites and suspicious downloads can reduce the risk of exploitation. Implementing endpoint detection and response (EDR) solutions capable of identifying anomalous browser behavior may help detect exploitation attempts. Finally, organizations should conduct vulnerability assessments and penetration testing to verify the absence of this vulnerability in their environments post-patching.