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FS#68462 - [samba] CVE-2020-14318 CVE-2020-14323 CVE-2020-14383

Attached to Project: Arch Linux
Opened by loqs (loqs) - Thursday, 29 October 2020, 11:50 GMT
Last edited by Jan de Groot (JGC) - Monday, 23 November 2020, 10:31 GMT
Task Type Bug Report
Category Security
Status Closed
Assigned To No-one
Architecture All
Severity High
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No


The SMB1/2/3 protocols have a concept of "ChangeNotify", where a client can request file name notification on a directory handle when a condition such as "new file creation" or "file size change" or "file timestamp update" occurs.
A missing permissions check on a directory handle requesting ChangeNotify meant that a client with a directory handle open only for FILE_READ_ATTRIBUTES (minimal access rights) could be used to obtain change notify replies from the server. These replies contain information that should not be available to directory handles open for FILE_READ_ATTRIBUTE only.

winbind in version 3.6 and later implements a request to translate multiple Windows SIDs into names in one request. This was done for performance reasons: Active Directory domain controllers can do multiple SID to name translations in one RPC call. It was an obvious extension to also offer this batch operation on the winbind unix domain stream socket that is available to local processes on the Samba server to reduce network round-trips to the domain controller.
Due to improper input validation a hand-crafted packet can make winbind perform a NULL pointer dereference and thus crash.

Some DNS records (such as MX and NS records) usually contain data in the additional section. Samba's dnsserver RPC pipe (which is an administrative interface not used in the DNS server itself) made an error in handling the case where there are no records present: instead of noticing the lack of records, it dereferenced uninitialised memory, causing the RPC server to crash. This RPC server, which also serves protocols other than dnsserver, will be restarted after a short delay, but it is easy for an authenticated non-admin attacker to crash it again as soon as it returns. The Samba DNS server itself will continue to operate, but many RPC services will not.

Additional info:
* samba 4.13.0-1
This task depends upon

Closed by  Jan de Groot (JGC)
Monday, 23 November 2020, 10:31 GMT
Reason for closing:  Fixed