An issue was discovered in tls_verify_crl in ProFTPD through 1.3.6b. A dereference of a NULL pointer may occur. This pointer is returned by the OpenSSL sk_X509_REVOKED_value() function when encountering an empty CRL installed by a system administrator. The dereference occurs when validating the certificate of a client connecting to the server in a TLS client/server mutual-authentication setup.
Exploitability
AV:NAC:LPR:HUI:NScope
S:UImpact
C:NI:NA:H4.9/CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H