Bug 1849509 (CVE-2020-10760)

Summary: CVE-2020-10760 samba: LDAP Use-after-free in Samba AD DC Global Catalog with paged_results and VLV
Product: [Other] Security Response Reporter: Huzaifa S. Sidhpurwala <huzaifas>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED NOTABUG QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: abokovoy, anoopcs, asn, gdeschner, hvyas, iboukris, iboukris, jarrpa, jstephen, lmohanty, madam, puebele, rhs-smb, sbose, security-response-team, ssorce, vbellur
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: samba 4.10.17, samba 4.11.11, samba 4.12.4 Doc Type: If docs needed, set a value
Doc Text:
A use-after-free flaw was found in samba LDAP server used in a AC DC configuration. A Samba LDAP user could use this flaw to crash samba.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2020-06-22 05:29:05 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1853276    
Bug Blocks: 1849490    

Description Huzaifa S. Sidhpurwala 2020-06-22 05:12:16 UTC 
As per upstream advisory:

Samba 4.5 and later implements VLV - Virtual List View, and Samba 4.10 and later reimplemented the paged_results control using similar code.

This code is more memory-efficient, storing only a pointer to the object, not the returned object.  However this means parts of the original request must be retained

When these controls are used by a client that connects to the Global Catalog server, these modules failed to correctly retain the control data along with the request, causing a use-after-free and an abort when this is detected by the talloc library.

NOTE WELL: Unsupported Samba versions before Samba 4.7 use a single process for the LDAP servers.

All versions of Samba after Samba 4.11 use the 'prefork' process model to create a shared connection pool.  Crashing servers are restarted, but service is disrupted.
Comment 1 Huzaifa S. Sidhpurwala 2020-06-22 05:13:45 UTC 
Acknowledgments:

Name: the Samba project
Upstream: Andrei Popa
Comment 4 Hardik Vyas 2020-06-23 08:48:04 UTC 
Statement:

This flaw does not affect the version of samba shipped with Red Hat Enterprise Linux and Red Hat Gluster Storage 3 because there is no support for samba as Active Directory Domain Controller.
Comment 5 Huzaifa S. Sidhpurwala 2020-07-02 09:34:31 UTC 
External References:

https://www.samba.org/samba/security/CVE-2020-10760.html
Comment 6 Huzaifa S. Sidhpurwala 2020-07-02 10:38:09 UTC 
Created samba tracking bugs for this issue:

Affects: fedora-all [bug 1853276]
Comment 7 Hardik Vyas 2020-07-02 11:34:06 UTC 
Upstream patch: https://github.com/samba-team/samba/commit/32c333def9ad5a1c67abee320cf5f3c4f2cb1e5c