CVE-2025-52496 is a high-severity vulnerability affecting Mbed TLS versions prior to 3.6.4. The issue arises from a race condition in the detection of AES-NI (Advanced Encryption Standard New Instructions) when certain compiler optimizations are applied. Specifically, this vulnerability is categorized under CWE-733, which involves compiler optimization removal or modification of security-critical code. The race condition occurs in multithreaded environments where the AES-NI detection logic can be disrupted, potentially allowing an attacker to extract AES encryption keys or perform Galois/Counter Mode (GCM) forgery attacks. AES-NI is a set of CPU instructions that accelerate AES encryption and decryption, and secure detection of its availability is critical for cryptographic operations. The vulnerability does not require user interaction or privileges but does require local access (AV:L) and has a high attack complexity (AC:H). The scope is changed (S:C), meaning the vulnerability can affect resources beyond the initially vulnerable component. The impact on confidentiality and integrity is high (C:H/I:H), while availability is not affected (A:N). No known exploits are currently reported in the wild, but the potential for key extraction and message forgery poses a significant risk to the confidentiality and integrity of encrypted communications relying on Mbed TLS in multithreaded applications.

For European organizations, this vulnerability could have severe consequences, especially for those relying on Mbed TLS in security-critical applications such as IoT devices, embedded systems, and network appliances. The ability to extract AES keys compromises the confidentiality of encrypted data, potentially exposing sensitive personal data protected under GDPR. GCM forgery attacks undermine data integrity, allowing attackers to manipulate encrypted messages undetected, which could lead to unauthorized transactions, data tampering, or disruption of secure communications. Industries such as finance, healthcare, telecommunications, and critical infrastructure in Europe are particularly at risk due to their reliance on strong cryptographic protections. The multithreaded nature of the vulnerability means that high-performance servers and applications using Mbed TLS in concurrent environments are vulnerable. This could lead to breaches of confidentiality and integrity, regulatory penalties, reputational damage, and operational disruptions.

European organizations should prioritize upgrading to Mbed TLS version 3.6.4 or later, where this vulnerability is addressed. Until patches are applied, organizations should audit their use of Mbed TLS in multithreaded contexts and consider disabling AES-NI optimizations if feasible, to mitigate the race condition risk. Implementing strict compiler settings to prevent aggressive optimizations that could remove or alter security-critical code is advisable. Additionally, organizations should conduct thorough code reviews and testing to detect any race conditions in cryptographic operations. Employing runtime protections such as thread synchronization mechanisms around AES-NI detection code can reduce the risk of exploitation. Monitoring cryptographic operations for anomalies and integrating intrusion detection systems that can identify unusual cryptographic failures or forgeries will help in early detection. Finally, organizations should ensure that cryptographic keys are managed securely and consider key rotation policies to limit exposure in case of compromise.