CVE-2026-28390

A flaw was found in OpenSSL. A remote attacker could exploit this vulnerability by sending a specially crafted Cryptographic Message Syntax (CMS) EnvelopedData message. During the processing of a KeyTransportRecipientInfo with RSA-OAEP encryption, the system attempts to access an optional parameter field without first verifying its presence. This leads to a NULL pointer dereference, which can cause applications processing the attacker-controlled CMS data to crash, resulting in a Denial of Service (DoS).

This CVE has been rated as moderate by redhat because the vulnerability is limited to a denial-of-service condition caused by a NULL pointer dereference in OpenSSL CMS processing, without evidence of memory corruption or code execution, furthermore the Affected functionality is niche. The vulnerable path requires: CMS/S/MIME processing, specifically CMS_decrypt(), with RSA-OAEP KeyTransportRecipientInfo. Many OpenSSL consumers never use CMS APIs, never process S/MIME, or do not decrypt attacker-controlled CMS objects. So exposure is far narrower than a generic TLS parsing vulnerability.

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.

Applications that process Cryptographic Message Syntax (CMS) EnvelopedData messages should be configured to only accept input from trusted sources. Restricting network access to services that process untrusted CMS data can also reduce exposure to this Denial of Service vulnerability.