CVE-2026-2781 is an integer overflow vulnerability located within the NSS Libraries component integrated into Mozilla Firefox. NSS is a critical security library that provides cryptographic services, and an integer overflow here can lead to memory corruption issues such as buffer overflows or improper memory allocation. These conditions can be exploited by attackers to execute arbitrary code, escalate privileges, or cause application crashes (denial of service). The vulnerability affects Firefox versions earlier than 148 and Firefox ESR versions earlier than 140.8, indicating that users running these versions are vulnerable. The integer overflow likely occurs during processing of specific data inputs handled by NSS, potentially involving cryptographic operations or certificate handling. Although no exploits have been reported in the wild yet, the nature of the vulnerability and the widespread use of Firefox make it a critical concern. The absence of a CVSS score suggests that the vulnerability is newly disclosed and pending further analysis. NSS is a foundational library used not only in Firefox but also in other applications, though this CVE specifically identifies Firefox as affected. The vulnerability was reserved and published in February 2026, indicating recent discovery and disclosure. The lack of patch links suggests that fixes may be forthcoming or in progress. Given the integral role of NSS in secure communications, exploitation could compromise confidentiality, integrity, and availability of user data and browser sessions.

The potential impact of CVE-2026-2781 is significant for organizations worldwide that rely on Mozilla Firefox for secure web browsing. Successful exploitation could allow attackers to execute arbitrary code within the context of the browser, potentially leading to system compromise, data theft, or persistent malware installation. This could undermine the confidentiality and integrity of sensitive information accessed via the browser, including credentials, financial data, and corporate resources. Additionally, exploitation could cause denial of service conditions, disrupting business operations. Since Firefox is widely used in both consumer and enterprise environments, the scope of affected systems is broad. Organizations in sectors such as finance, government, healthcare, and critical infrastructure are particularly at risk due to their reliance on secure communications and the high value of their data. The vulnerability could also be leveraged in targeted attacks or supply chain compromises. The absence of known exploits currently provides a window for proactive mitigation, but the risk of future exploitation remains high.

To mitigate CVE-2026-2781, organizations should prioritize updating Mozilla Firefox to version 148 or later, or Firefox ESR 140.8 or later, as soon as these patches become available. Until patches are released, organizations should consider temporary mitigations such as restricting access to untrusted websites, disabling or limiting the use of NSS-dependent features if feasible, and monitoring network traffic for suspicious activity. Employing endpoint detection and response (EDR) tools to detect anomalous behavior related to memory corruption or exploitation attempts can provide early warning. Security teams should also review browser usage policies to ensure timely updates and educate users about the risks of using outdated software. Additionally, organizations should maintain robust backup and recovery procedures to mitigate potential damage from exploitation. Monitoring Mozilla security advisories and threat intelligence feeds will be critical to respond promptly to any emerging exploit campaigns. Network segmentation and application whitelisting can further reduce exposure. Finally, conducting internal vulnerability assessments and penetration testing can help identify any residual risks related to this vulnerability.