CVE-2026-42768

A flaw was found in OpenSSL's CMS_decrypt() and PKCS7_decrypt() functions. This vulnerability, a Bleichenbacher-style oracle, could allow a remote attacker to decrypt or sign messages using the victim's private RSA key. Exploitation requires the attacker to provide specially crafted CMS or S/MIME messages and observe the application's error codes or decryption output. While the attack is technically possible, the specific conditions required make it unlikely to be exploited in typical deployments.

This Low severity vulnerability in OpenSSL's CMS_decrypt() and PKCS7_decrypt() functions exposes a Bleichenbacher-style oracle. Exploitation requires an attacker to control input CMS/S/MIME messages and observe decryption errors or output, a scenario deemed unlikely in most Red Hat product deployments. The attack could allow decryption or signing of messages with a victim's private RSA key.

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 vulnerability, applications utilizing CMS_decrypt() or PKCS7_decrypt() should ensure a recipient certificate is always provided to identify the specific RecipientInfo for decryption. This practice helps prevent the Bleichenbacher-style oracle attack by ensuring proper key identification.