All versions of Samba prior to 4.13.17 are vulnerable to an out-of-bounds heap read write vulnerability that allows remote attackers to execute arbitrary code as root on affected Samba installations that use the VFS module vfs_fruit.
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== Subject: Out-of-bounds heap read/write vulnerability
== in VFS module vfs_fruit allows code execution
==
== CVE ID#: CVE-2021-44142
==
== Versions: All versions of Samba prior to 4.13.17
==
== Summary: This vulnerability allows remote attackers to
== execute arbitrary code as root on affected Samba
== installations that use the VFS module vfs_fruit.
=================================================================
===========
Description
===========
All versions of Samba prior to 4.13.17 are vulnerable to an
out-of-bounds heap read write vulnerability that allows remote
attackers to execute arbitrary code as root on affected Samba
installations that use the VFS module vfs_fruit.
The specific flaw exists within the parsing of EA metadata when
opening files in smbd. Access as a user that has write access to a
file's extended attributes is required to exploit this
vulnerability. Note that this could be a guest or unauthenticated user
if such users are allowed write access to file extended attributes.
The problem in vfs_fruit exists in the default configuration of the
fruit VFS module using fruit:metadata=netatalk or fruit:resource=file.
If both options are set to different settings than the default values,
the system is not affected by the security issue.
==================
Patch Availability
==================
Patches addressing both these issues have been posted to:
https://www.samba.org/samba/security/
Additionally, Samba 4.13.17, 4.14.12 and 4.15.5 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:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:F/RL:O/RC:C
Base score 9.9.
==========
Workaround
==========
As a workaround remove the "fruit" VFS module from the list of
configured VFS objects in any "vfs objects" line in the Samba
configuration smb.conf.
Note that changing the VFS module settings fruit:metadata or
fruit:resource to use the unaffected setting causes all stored
information to be inaccessible and will make it appear to macOS
clients as if the information is lost.
=======
Credits
=======
Originally reported by Orange Tsai from DEVCORE.
Patches provided by Ralph Böhme of the Samba team.
==========================================================
== Our Code, Our Bugs, Our Responsibility.
== The Samba Team
==========================================================