Attachment 18021 Details for Bug 15439 – Advisory v1

Advisory v1

advisory-CVE-2023-4091.txt (text/plain), 2.29 KB, created by Ralph Böhme on 2023-08-03 09:39:23 UTC

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Creator: Ralph Böhme

Created: 2023-08-03 09:39:23 UTC

Size: 2.29 KB

patch

obsolete

>
>
>TODO: VERSION
>
>
>===========================================================
>== Subject:     SMB clients can truncate files with
>==              read-only permissions
>==
>== CVE ID#:     CVE-2023-4091
>==
>== Versions:    All Samba versions
>==
>== Summary:     SMB client can truncate files to 0 bytes
>==              by opening files with OVERWRITE disposition
>==              when using the acl_xattr Samba VFS module
>==              with the smb.conf setting
>==              "acl_xattr:ignore system acls = yes"
>===========================================================
>
>===========
>Description
>===========
>
>SMB allows opening files for read-only and truncating the
>opened files by specifying an OVERWRITE create
>disposition. This operation requires write access to the
>file, but Samba incorrectly checks the requested read-only
>permission on the files ACL, instead of the required
>read/write permission.
>
>When opening the system file handle, Samba internally opens
>the file in read/write mode as that is required by POSIX
>when passing O_TRUNC. Therefor most default Samba configurations
>are not affected by this security vulnerability.
>
>Affected Samba configurations are ones where somehow kernel
>file-system permission checks are bypassed, relying on
>Samba's own permission enforcement.
>
>The widely used Samba VFS module "acl_xattr" when configured
>with the module configuration parameter "acl_xattr:ignore
>system acls = yes" is the only upstream Samba module that
>allows this behavior and is affected by this vulnerability.
>
>
>==================
>Patch Availability
>==================
>
>Patches addressing both these issues have been posted to:
>
>    https://www.samba.org/samba/security/
>
>Additionally, Samba $VERSIONS 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:U/C:N/I:H/A:N (6.5)
>
>==========
>Workaround
>==========
>
>None.
>
>=======
>Credits
>=======
>
>Originally reported by $REPORTER.
>
>Patches provided by Ralph BÃ¶hme of SerNet and the Samba team.
>
>==========================================================
>== Our Code, Our Bugs, Our Responsibility.
>== The Samba Team
>==========================================================
>

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