Researchers have published findings on vulnerabilities in NFC technologies, specifically targeting MIFARE Ultralight C, MIFARE Ultralight AES, and NTAG 223/224 DNA cards. These cards are widely used in access control, ticketing, and hospitality. The research reveals how attackers can weaken security through relay attacks and key overwrites, making key recovery feasible with modest resources.

The core issue stems from design choices that allow unauthenticated memory writes. The study found that many deployments fail to configure security features, such as lock bytes and key diversification. For example, the default factory key in MIFARE Ultralight C, which spells out "BREAKMEIFYOUCAN!", highlights the potential for exploitation if not properly secured.

Attackers can reduce the keyspace of two-key 3DES from 2^112 to 2^28, making brute-force attacks possible. Non-NXP compatible cards are particularly vulnerable, with key recovery possible in under a minute. The research also demonstrated credential forgery in a real hospitality system.

The findings underscore the importance of proper configuration and security best practices. Those using these systems should audit their deployments. The researchers responsibly disclosed their findings to NXP. They recommend using key diversification, locking memory pages, and verifying genuine NXP chips to mitigate risks related to NFC security.