CVE-2026-28389

Issue summary: During processing of a crafted CMS EnvelopedData message with KeyAgreeRecipientInfo a NULL pointer dereference can happen. Impact summary: Applications that process attacker-controlled CMS data may crash before authentication or cryptographic operations occur resulting in Denial of Service. When a CMS EnvelopedData message that uses KeyAgreeRecipientInfo is processed, the optional parameters field of KeyEncryptionAlgorithmIdentifier is examined without checking for its presence. This results in a NULL pointer dereference if the field is missing. Applications and services that call CMS_decrypt() on untrusted input (e.g., S/MIME processing or CMS-based protocols) are vulnerable. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

We have discovered 87,429 live websites that are affected by CVE-2026-28389.

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Affected Software

Product	OpenSSL
Category	Web Server Extensions
Vulnerable Domains	87,429 live websites (18% of OpenSSL install base)
Vulnerable Versions	from 3 through 3.0.20 from 3.3 through 3.3.7 from 3.4 through 3.4.5 from 3.5 through 3.5.6 from 3.6 through 3.6.2
Vulnerable Versions Count	35 versions ( 48% of all versions)