NULL pointer de-reference and use-after-free

Description

Samba has, since Samba 4.5, supported the VLV Active Directory LDAP
feature, to allow clients to obtain ‘virtual list views’ of search
results against a Samba AD DC using an LDAP control.

The combination of this control, and the ASQ control combines to allow
an authenticated user to trigger a NULL-pointer de-reference. It is
also possible to trigger a use-after-free, both as the code is very
similar to that addressed by CVE-2020-10700 and due to the way
errors are handled in the dsdb_paged_results module since Samba 4.10.

Patch Availability

Patches addressing both of these issues have been posted to:

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

Additionally, Samba 4.10.17, 4.11.11 and 4.12.4 have been issued
as security releases to correct the defect. Samba administrators are
advised to upgrade to these releases or apply the patch as soon
as possible.

CVSSv3 calculation

CVSS:v3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (6.5)

Workaround and mitigation

None.

Credits

Originally reported by Andrew Bartlett of Catalyst and the Samba Team.

Patches provided by Andrew Bartlett and Gary Lockyer of Catalyst and
the Samba Team.

== Our Code, Our Bugs, Our Responsibility.
== The Samba Team