CVE-2026-75803

A flaw in OpenSSL causes EVP_Cipher() to skip AEAD tag verification for ChaCha20-Poly1305 and AES-OCB ciphers when decrypting empty ciphertexts. This allows remote attackers to submit forged messages that affected applications incorrectly accept as valid.

Red Hat rates this as Low since exploitation requires a rare API misuse pattern using EVP_Cipher() with empty ChaCha20-Poly1305 or AES-OCB ciphertexts. Standard TLS implementations and typical EVP_Decrypt* workflows are unaffected, resulting in High Attack Complexity. Bypassing tag verification under these narrow conditions permits limited message forgery (Low Integrity) without exposing secrets (No Confidentiality Impact). Additionally, OpenSSL FIPS modules remain unaffected as they do not include these ciphers.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this ensure that all integrity check values present in messages are properly checked in accordance with the protocol specification before they are parsed and used. Applications must rigorously calculate the checksum and explicitly verify that the received integrity value matches the calculated one to prevent malicious data injection.