=========================================================== == Subject: Use-after-free in Samba AD DC LDAP Server with ASQ == == CVE ID#: CVE-2020-10700 == == Versions: Samba 4.10.0 and later == == Summary: A client combining the 'ASQ' and 'Paged Results' LDAP controls can cause a use-after-free in Samba's AD DC LDAP server =========================================================== =========== Description =========== Samba has, since Samba 4.0, supported the Paged Results LDAP feature, to allow clients to obtain pages of search results against a Samba AD DC using an LDAP control. Since Samba 4.7.11 and 4.8.6 a Denial of Service prevention has been in place in this module, to age out old client requests if more than 10 such requests are outstanding. A rewrite of the module for more efficient memory handling in Samba 4.11 changed the module behaviour, and combined with the above to introduce the use-after-free. The use-after-free occurs when the 'Paged Results' control is combined with the 'ASQ' control, another Active Directory LDAP feature. ================== Patch Availability ================== Patches addressing both of these issues have been posted to: https://www.samba.org/samba/security/ Additionally, Samba 4.10.15, 4.11.8 and 4.12.2 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:3.1:AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H (5.3) ================================ Workaround or mitigating factors ================================ The crash is hard to trigger, and relies in particular on the chain of child and grandchild links being queried with ASQ. Malicious users without write access will need to find a suitable chain within the existing directory layout. ======= Credits ======= Originally reported by Andrei Popa <andrei.popa@next-gen.ro>. Patches provided by Andrew Bartlett of Catalyst and the Samba team. ========================================================== == Our Code, Our Bugs, Our Responsibility. == The Samba Team ==========================================================