CVE-2026-75803

Issue summary: ChaCha20-Poly1305 and AES-OCB decryption with an empty

ciphertext can report success without verifying the supplied authentication

tag when the operation is finalized by calling the EVP_Cipher() function.

Impact summary: Applications calling EVP_Cipher() on an empty ciphertext and

expecting the call to check the AEAD tag may accept forged messages.

CWE: CWE-354 (Improper Validation of Integrity Check Value)

Description: The EVP_Cipher() API call for AEAD ciphers behaves like a one

shot encryption and decryption call. It also verifies the AEAD tag after the

decryption operation. However for AES-OCB and ChaCha20-Poly1305 ciphers

it skipped the AEAD tag verification when an empty ciphertext was passed to

the function. The callers of this function might believe that a successful

return indicates a valid AEAD tag for these ciphers, even when that has not

truly been validated in this case.

FIPS impact: no

The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this CVE

as the affected algorithms are not FIPS approved and thus not implemented

in the FIPS module.