CVE-2026-45445 is a cryptographic vulnerability in OpenSSL’s AES-OCB mode where the Initialisation Vector (IV) is silently ignored when encryption or decryption is performed via the EVP_Cipher() API path. This means data intended to be protected with a unique IV may be encrypted with a predictable or reused nonce, undermining the confidentiality and integrity guarantees of AES-OCB. Any Azure service or workload relying on OpenSSL’s EVP_Cipher() with AES-OCB mode is potentially at risk of ciphertext forgery or plaintext recovery.

Security Architect’s Take: Audit workloads and Azure-hosted applications that use OpenSSL’s EVP_Cipher() with AES-OCB mode and prioritise patching to a remediated OpenSSL version as soon as Microsoft and upstream OpenSSL publish fixes. If AES-OCB is not a hard requirement, consider migrating to AES-GCM via the EVP_AEAD API as an interim risk reduction measure.

Original advisory: CVE-2026-45445 AES-OCB IV Ignored on EVP_Cipher() Path