Samba NDR Parsing ndr_pull_dnsp_name Heap-based Buffer

Description

The Samba routine ndr_pull_dnsp_name contains an integer wrap problem,
leading to an attacker-controlled memory overwrite. ndr_pull_dnsp_name
parses data from the Samba Active Directory ldb database. Any user
who can write to the dnsRecord attribute over LDAP can trigger this
memory corruption.

By default, all authenticated LDAP users can write to the dnsRecord
attribute on new DNS objects. This makes the defect a remote privilege
escalation.

Patch Availability

A patch addressing this defect has been posted to

https://www.samba.org/samba/security/

Additionally, Samba 4.5.3, 4.4.8 and 4.3.13 have been issued as
security releases to correct the defect. Samba vendors and administrators
running affected versions are advised to upgrade or apply the patch as
soon as possible.

Workaround

It is possible to change the ntSecurityDescriptor on DNS zones, but
this will impact on the expected behaviour of the AD Domain.

Credits

This vulnerability was detected and reported to the Samba developers
by Trend Micro’s Zero Day Initiative and Frederic Besler.