CVE-2023-4091: Samba: smb clients can truncate files with read-only permissions
First published: Tue Oct 03 2023(Updated: )
A vulnerability was discovered in Samba, where the flaw allows SMB clients to truncate files, even with read-only permissions when the Samba VFS module "acl_xattr" is configured with "acl_xattr:ignore system acls = yes". The SMB protocol allows opening files when the client requests read-only access but then implicitly truncates the opened file to 0 bytes if the client specifies a separate OVERWRITE create disposition request. The issue arises in configurations that bypass kernel file system permissions checks, relying solely on Samba's permissions.
Credit: secalert@redhat.com secalert@redhat.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Samba Samba | <4.17.12 | |
| Samba Samba | >=4.18.0<4.18.8 | |
| Samba Samba | >=4.19.0<4.19.1 | |
| Fedoraproject Fedora | =39 | |
| Redhat Storage | =3.0 | |
| Redhat Enterprise Linux | =8.0 | |
| Redhat Enterprise Linux Eus | =9.0 | |
| redhat/samba | <4.19.1 | 4.19.1 |
| redhat/samba | <4.18.8 | 4.18.8 |
| redhat/samba | <4.17.12 | 4.17.12 |
| ubuntu/samba | <2:4.15.13+dfsg-0ubuntu0.20.04.6 | 2:4.15.13+dfsg-0ubuntu0.20.04.6 |
| ubuntu/samba | <2:4.15.13+dfsg-0ubuntu1.5 | 2:4.15.13+dfsg-0ubuntu1.5 |
| ubuntu/samba | <2:4.17.7+dfsg-1ubuntu2.3 | 2:4.17.7+dfsg-1ubuntu2.3 |
| ubuntu/samba | <2:4.18.6+dfsg-1ubuntu2.1 | 2:4.18.6+dfsg-1ubuntu2.1 |
| debian/samba | <=2:4.9.5+dfsg-5+deb10u3<=2:4.13.13+dfsg-1~deb11u5 | 2:4.9.5+dfsg-5+deb10u5 2:4.13.13+dfsg-1~deb11u6 2:4.17.12+dfsg-0+deb12u1 2:4.19.5+dfsg-1 2:4.19.6+dfsg-1 |
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Reference Links
- https://access.redhat.com/errata/RHSA-2023:6209
- https://access.redhat.com/errata/RHSA-2023:6744
- https://access.redhat.com/errata/RHSA-2023:7371
- https://access.redhat.com/errata/RHSA-2023:7408
- https://access.redhat.com/errata/RHSA-2023:7464
- https://access.redhat.com/errata/RHSA-2023:7467
- https://access.redhat.com/security/cve/CVE-2023-4091
- https://bugzilla.redhat.com/show_bug.cgi?id=2241882
- https://bugzilla.samba.org/show_bug.cgi?id=15439
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZUMVALLFFDFC53JZMUWA6HPD7HUGAP5I/
- https://security.netapp.com/advisory/ntap-20231124-0002/
- https://www.samba.org/samba/security/CVE-2023-4091.html
- https://launchpad.net/bugs/cve/CVE-2023-4091
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=2243231
- https://ubuntu.com/security/notices/USN-6425-1
- https://ubuntu.com/security/notices/USN-6425-3
- https://www.cve.org/CVERecord?id=CVE-2023-4091
- https://nvd.nist.gov/vuln/detail/CVE-2023-4091
- https://security-tracker.debian.org/tracker/CVE-2023-4091
- https://ubuntu.com/security/CVE-2023-4091
- https://git.samba.org/?p=samba.git;a=commit;h=b08a60160e6ab8d982d31844bcbf7ab67ff3a8de
- https://git.samba.org/?p=samba.git;a=commit;h=8b26f634372f11edcbea33dfd68a3d57889dfcc5
- https://lists.debian.org/debian-lts-announce/2024/04/msg00015.html
Frequently Asked Questions
What is CVE-2023-4091?
CVE-2023-4091 is a vulnerability that allows SMB clients to truncate files with read-only permissions.
How does CVE-2023-4091 impact SMB clients?
CVE-2023-4091 allows SMB clients to truncate files even if they only have read-only permissions.
Which software is affected by CVE-2023-4091?
Samba versions up to 2:4.15.13+dfsg-0ubuntu0.20.04.6, 2:4.15.13+dfsg-0ubuntu1.5, and 2:4.17.7+dfsg-1ubuntu2.3 are affected by CVE-2023-4091.
How can I fix CVE-2023-4091?
To fix CVE-2023-4091, update Samba to version 2:4.15.13+dfsg-0ubuntu0.20.04.6, 2:4.15.13+dfsg-0ubuntu1.5, or 2:4.17.7+dfsg-1ubuntu2.3 depending on your Ubuntu release.
Where can I find more information about CVE-2023-4091?
You can find more information about CVE-2023-4091 on the MITRE CVE website (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-4091), the Samba security page (https://www.samba.org/samba/security/CVE-2023-4091.html), and the Ubuntu security notices (https://ubuntu.com/security/notices/USN-6425-1).
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