A flaw was found in the way an LDAP search expression could crash the shared LDAP server process of a samba AD DC in samba before version 4.10. An authenticated user, having read permissions on the LDAP server, could use this flaw to cause denial of service.

Samba from version 4.9.0 and before version 4.9.3 that have AD DC configurations watching for bad passwords (to restrict brute forcing of passwords) in a window of more than 3 minutes may not watch for bad passwords at all. The primary risk from this issue is with regards to domains that have been upgraded from Samba 4.8 and earlier. In these cases the manual testing done to confirm an organisation's password policies apply as expected may not have been re-done after the upgrade.

Samba from version 4.7.0 has a vulnerability that allows a user in a Samba AD domain to crash the KDC when Samba is built in the non-default MIT Kerberos configuration. With this advisory the Samba Team clarify that the MIT Kerberos build of the Samba AD DC is considered experimental. Therefore the Samba Team will not issue security patches for this configuration. Additionally, Samba 4.7.12, 4.8.7 and 4.9.3 have been issued as security releases to prevent building of the AD DC with MIT Kerberos unless --with-experimental-mit-ad-dc is specified to the configure command.

Samba from version 4.9.0 and before version 4.9.3 is vulnerable to a NULL pointer de-reference. During the processing of an DNS zone in the DNS management DCE/RPC server, the internal DNS server or the Samba DLZ plugin for BIND9, if the DSPROPERTY_ZONE_MASTER_SERVERS property or DSPROPERTY_ZONE_SCAVENGING_SERVERS property is set, the server will follow a NULL pointer and terminate. There is no further vulnerability associated with this issue, merely a denial of service.

Samba from version 4.0.0 and before versions 4.7.12, 4.8.7, 4.9.3 is vulnerable to a denial of service. During the processing of an LDAP search before Samba's AD DC returns the LDAP entries to the client, the entries are cached in a single memory object with a maximum size of 256MB. When this size is reached, the Samba process providing the LDAP service will follow the NULL pointer, terminating the process. There is no further vulnerability associated with this issue, merely a denial of service.

Samba from version 4.3.0 and before versions 4.7.12, 4.8.7 and 4.9.3 are vulnerable to a denial of service. When configured to accept smart-card authentication, Samba's KDC will call talloc_free() twice on the same memory if the principal in a validly signed certificate does not match the principal in the AS-REQ. This is only possible after authentication with a trusted certificate. talloc is robust against further corruption from a double-free with talloc_free() and directly calls abort(), terminating the KDC process.

A denial of service vulnerability was discovered in Samba's LDAP server before versions 4.7.12, 4.8.7, and 4.9.3. A CNAME loop could lead to infinite recursion in the server. An unprivileged local attacker could create such an entry, leading to denial of service.

Unspecified vulnerability on HP NonStop Servers with software H06.x through H06.23.00 and J06.x through J06.12.00, when Samba is used, allows remote authenticated users to execute arbitrary code via unknown vectors.