CVE-2026-4648 in NFC Wristbands
Summary
by MITRE • 07/28/2026
Use of an insecure cryptographic algorithm in the cashless payment system using NFC wristbands from CasfID Servicios Tecnológicos S.L.U. (version used at Resurrection Fest 2025), which employs cards based on MIFARE Classic technology (FM11RF08S). The cryptographic weakness of the authentication algorithm allows an attacker to retrieve access keys using techniques known as Backdoored Nested Attack, read the wristband’s entire contents, and clone its credentials onto a compatible rewritable card. Exploitation of this vulnerability could enable the impersonation of other attendees, the fraudulent use of the balance associated with their wristbands, and financial losses for both the affected users and the event organizers.
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Analysis
by VulDB Data Team • 07/28/2026
The vulnerability in question involves a critical cryptographic weakness within the cashless payment infrastructure deployed at Resurrection Fest 2025 by CasfID Servicios Tecnológicos S.L.U. This system utilizes MIFARE Classic technology specifically the FM11RF08S chip variant which employs a fundamentally flawed authentication mechanism that has been extensively documented as insecure. The implementation relies on the legacy MIFARE Classic crypto1 algorithm that was designed with inadequate security parameters and has been proven vulnerable to various attack vectors since its initial release in 2000.
The core technical flaw lies in the cryptographic implementation of the MIFARE Classic authentication protocol which uses a 48-bit cipher key that can be brute-forced within reasonable timeframes using modern computational resources. Attackers can exploit this weakness through techniques such as the Backdoored Nested Attack that leverages the predictable nature of the crypto1 algorithm to recover the original authentication keys. This attack method specifically targets the way the system handles nested authentication challenges and allows an attacker with proximity access to a valid card to extract both the master key and individual sector keys in a systematic manner.
The operational impact of this vulnerability extends far beyond simple data theft, creating substantial financial risks for both attendees and event organizers. Once an attacker successfully extracts the cryptographic keys through nested attacks, they can completely read all data stored on the wristband including user identification information, account balances, transaction history, and potentially personal details. The cloned credentials can then be used to impersonate legitimate users throughout the event, enabling unauthorized access to payment systems and the ability to drain account balances. This creates a cascading effect where multiple attendees may experience financial losses simultaneously while the organizers face potential liability issues and reputational damage.
The security implications of this vulnerability align with several CWE classifications including CWE-327 which addresses use of a broken or weak cryptographic algorithm, and CWE-310 which covers lack of entropy in a random number generator. From an ATT&CK framework perspective, this vulnerability maps to techniques such as credential access through exploitation of weak encryption and privilege escalation via cloned credentials, with potential lateral movement opportunities within the payment ecosystem. The attack surface is further expanded by the fact that MIFARE Classic technology has been widely deployed across various industries including transportation, access control, and event management systems, making this vulnerability particularly concerning for organizations that have not upgraded to more secure technologies.
Mitigation strategies should prioritize immediate replacement of all affected MIFARE Classic cards with secure alternatives such as MIFARE DESFire or other modern cryptographic solutions that implement robust key management protocols. Organizations must also implement monitoring systems to detect unusual transaction patterns that might indicate credential cloning activities. The deployment of network segmentation and real-time transaction validation can help minimize the impact if an attacker successfully clones credentials, while comprehensive key rotation procedures should be established for any remaining legacy systems. Additionally, all personnel handling these systems should receive security training on recognizing social engineering attacks that might facilitate physical access to target cards, as proximity-based attacks often require minimal technical expertise but significant physical access opportunities.
The broader industry implications of this vulnerability highlight the persistent issue of legacy technology deployment in critical infrastructure environments where security updates are often delayed or ignored due to cost considerations or compatibility concerns. This case demonstrates how seemingly minor cryptographic weaknesses can create substantial financial and operational risks when deployed at large-scale events where multiple users interact with shared payment systems, emphasizing the need for regular security assessments and proactive migration strategies for outdated cryptographic implementations.