Samba Vulnerability Leads to DoS in DNServer and Can Crash Active Directory Services

Samba released security updates for a couple of vulnerabilities that could cause Denial of Service in dnsserver and LDAP server crash.

Denial of Service in DNS Server

The vulnerability allows an authenticated user to crash the RPC server via a NULLpointer de-reference. The DNS server RPC provides admin access to manager DNS records and zones.

Following are the affected Samba version 4.9 and 4.10, and it has been fixed with Samba 4.9.9 and 4.10.5. The vulnerability can be tracked as CVE-2019-12435 and has CVSS:3.0 severity score 6.5.

Samba also suggested a workaround by setting ‘dcerpc endpoint servers = -dnsserver‘ in the smb.conf and restarting Samba.

LDAP server crash

All the versions of Samba since 4.10.0 are affected with the vulnerability, a user with read access can crash the LDAP server process, but it depends on the Samba version and process model, “this may crash only the user’s own connection.”

“Specifically, while in Samba 4.10, the default is for one process per connected client, site-specific configuration trigger can change this.”

Samba versions since 4.10.0 are affected, and it has been fixed with 4.10.5. The vulnerability can be tracked as CVE-2019-12436 and has CVSS:3.0 severity score 6.5.

Samba suggested a workaround “return to the default configuration by running ‘samba’ with -M standard, however, this may consume more memory and would not address the \DC\homes issue.”

Administrators are recommended to update this release or apply the patch as soon as possible to address Samba Vulnerability.