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, the vulnerability is classified under CWE-733, which involves compiler optimization removal or modification of security-critical code. This flaw can lead to two critical security risks: first, an attacker may be able to extract AES encryption keys from a multithreaded program using Mbed TLS, and second, the attacker could perform a Galois/Counter Mode (GCM) forgery, compromising message integrity. The race condition likely occurs because the AES-NI detection code is not properly synchronized across threads, and compiler optimizations may remove or reorder critical security checks or code paths, weakening the cryptographic protections. The vulnerability has a CVSS v3.1 base score of 7.8, indicating high severity. The vector string (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N) shows that the attack requires local access (AV:L), high attack complexity (AC:H), no privileges (PR:N), no user interaction (UI:N), and the scope is changed (S:C), with high impact on confidentiality and integrity but no impact on availability. No known exploits are currently reported in the wild, and no official patches are linked yet, but upgrading to Mbed TLS 3.6.4 or later is implied as the fix. This vulnerability is particularly dangerous in multithreaded environments where cryptographic operations rely on AES-NI acceleration, as it could allow attackers to bypass cryptographic protections by exploiting timing or synchronization flaws introduced or exacerbated by compiler optimizations.

For European organizations, the impact of CVE-2025-52496 is significant, especially for those relying on Mbed TLS in multithreaded applications that use AES encryption with AES-NI acceleration. Confidentiality is severely compromised since AES keys could be extracted, potentially exposing sensitive data such as personal information, financial records, or intellectual property. Integrity is also at risk due to the possibility of GCM forgery, which could allow attackers to tamper with encrypted communications or data without detection. This undermines trust in secure communications, digital signatures, and data protection mechanisms. The vulnerability does not affect availability directly but the loss of confidentiality and integrity can lead to regulatory non-compliance under GDPR and other European data protection laws, resulting in legal and financial penalties. Sectors such as finance, healthcare, telecommunications, and critical infrastructure, which often use Mbed TLS for embedded or IoT devices, are particularly vulnerable. The requirement for local access and high attack complexity somewhat limits remote exploitation, but insider threats or compromised local systems could still exploit this flaw. The multithreaded nature of the vulnerability means that high-performance or parallelized cryptographic operations are at risk, which are common in modern European enterprise environments.

European organizations should immediately audit their use of Mbed TLS, especially in multithreaded applications utilizing AES-NI. They should upgrade to Mbed TLS version 3.6.4 or later as soon as it becomes available, as this version addresses the race condition and compiler optimization issues. Until patches are applied, organizations should consider disabling AES-NI acceleration if feasible, to avoid triggering the vulnerable code paths, though this may impact performance. Additionally, compile-time flags should be reviewed to disable aggressive compiler optimizations that might remove or reorder security-critical code. Implementing strict code review and testing procedures for cryptographic modules in multithreaded contexts can help detect similar issues. Monitoring local system access and restricting it to trusted users can reduce the risk of exploitation. Organizations should also enhance logging and anomaly detection for cryptographic operations to identify potential key extraction or forgery attempts. Finally, vendors and developers should be engaged to prioritize patch deployment and provide guidance on secure compilation and threading practices.