The mbedtls update to version 3.6.6 (LTS maintenance update from 3.6.1) fixes several security issues discovered across versions 3.6.2 to 3.6.6. Notable vulnerabilities include CVE-2024-49195 (buffer underrun in pkwrite), CVE-2025-27809 (certificate verification accepting arbitrary hostnames), CVE-2025-27810 (possible authentication bypass on failed memory allocation or hardware errors), timing side channels in PKCS#7 padding removal and RSA operations, race conditions in AES-NI support detection leading to key extraction or forgery, padding-oracle attacks, and RNG state duplication across process forks and VM cloning. These flaws impact cryptographic integrity, authentication, and confidentiality.

Exploitation of these vulnerabilities could allow attackers to bypass authentication, perform man-in-the-middle downgrade attacks, extract cryptographic keys, cause signature verification bypass, trigger memory corruption, and exploit timing side channels to leak sensitive information. The issues affect core cryptographic functions and could compromise secure communications and data protection relying on mbedtls.

A security update to mbedtls version 3.6.6 is available that addresses all listed vulnerabilities. Users and administrators should upgrade to this version promptly to mitigate these critical security risks. No additional vendor advisory information is provided, so patch status beyond this update is not confirmed.