Bug 1691518 (CVE-2019-3880) - CVE-2019-3880 samba: save registry file outside share as unprivileged user
Summary: CVE-2019-3880 samba: save registry file outside share as unprivileged user
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2019-3880
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1696524 1696525 1696577 1697717
Blocks: 1691522
TreeView+ depends on / blocked
 
Reported: 2019-03-21 19:42 UTC by Laura Pardo
Modified: 2021-02-16 22:13 UTC (History)
27 users (show)

Fixed In Version: samba 4.8.11, samba 4.9.6, samba 4.10.2
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in the way samba implemented an RPC endpoint emulating the Windows registry service API. An unprivileged attacker could use this flaw to create a new registry hive file anywhere they have unix permissions which could lead to creation of a new file in the Samba share.
Clone Of:
Environment:
Last Closed: 2019-07-30 13:18:30 UTC
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2019:1966 0 None None None 2019-07-30 10:04:19 UTC
Red Hat Product Errata RHSA-2019:1967 0 None None None 2019-07-30 10:22:13 UTC
Red Hat Product Errata RHSA-2019:2099 0 None None None 2019-08-06 12:13:51 UTC
Red Hat Product Errata RHSA-2019:3582 0 None None None 2019-11-05 21:14:27 UTC
Samba Project 13851 0 None None None 2019-07-29 11:36:35 UTC

Description Laura Pardo 2019-03-21 19:42:44 UTC 
As per samba upstream advisory:

Samba contains an RPC endpoint emulating the Windows registry service API. One of the requests, "winreg_SaveKey", is susceptible to a path/symlink traversal vulnerability. Unprivileged users can use it to create a new registry hive file anywhere they have unix permissions to create a new file within a Samba share. If they are able to create symlinks on a Samba share, they can create a new registry hive file anywhere they have write access, even outside a Samba share definition.

Note - existing share restrictions such as "read only" or share ACLs do *not* prevent new registry hive files being written to the filesystem. A file may be written under any share definition wherever the user has unix permissions to create a file.

Existing files cannot be overwritten using this vulnerability, only new registry hive files can be created, however the presence of existing files with a specific name can be detected.

Samba writes or detects the file as the authenticated user, not as root.
Comment 1 Laura Pardo 2019-03-21 19:45:14 UTC 
Acknowledgments:

Name: Michael Hanselmann
Comment 2 Dave Baker 2019-03-27 20:05:19 UTC 
openshift-online-3 does not provision samba endpoints.
Comment 5 Huzaifa S. Sidhpurwala 2019-04-05 06:00:45 UTC 
Note: 

This affects not only Linux <> Windows configurations but may also affect Linux <> Linux configurations using Samba as RPC endpoints. (since winreg_SaveKey RPC call is also implemented on the client side)
Comment 7 Huzaifa S. Sidhpurwala 2019-04-05 06:07:45 UTC 
Mitigation:

Either turn off SMB1 by setting the global parameter:
'min protocol = SMB2'
or if SMB1 is required turn off unix extensions by setting the global parameter:
'unix extensions = no'
in the smb.conf file.
Comment 11 Doran Moppert 2019-04-09 04:04:48 UTC 
External References:

https://www.samba.org/samba/security/CVE-2019-3880.html
Comment 12 Doran Moppert 2019-04-09 04:05:08 UTC 
Created samba tracking bugs for this issue:

Affects: fedora-all [bug 1697717]
Comment 13 Hardik Vyas 2019-04-09 06:04:04 UTC 
Statement:

This issue affects the version of samba shipped with Red Hat Gluster Storage 3, as it contains the vulnerable functionality.
Comment 15 errata-xmlrpc 2019-07-30 10:04:18 UTC 
This issue has been addressed in the following products:

  Red Hat Gluster Storage 3.4 for RHEL 7

Via RHSA-2019:1966 https://access.redhat.com/errata/RHSA-2019:1966
Comment 16 errata-xmlrpc 2019-07-30 10:22:12 UTC 
This issue has been addressed in the following products:

  Red Hat Gluster Storage 3.4 for RHEL 6

Via RHSA-2019:1967 https://access.redhat.com/errata/RHSA-2019:1967
Comment 17 Product Security DevOps Team 2019-07-30 13:18:30 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2019-3880
Comment 18 errata-xmlrpc 2019-08-06 12:13:49 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2019:2099 https://access.redhat.com/errata/RHSA-2019:2099
Comment 19 errata-xmlrpc 2019-11-05 21:14:25 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2019:3582 https://access.redhat.com/errata/RHSA-2019:3582
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