CVE-2023-4091

Samba: smb clients can truncate files with read-only permissions

Published Nov 3, 2023 CVSS 3.1 · 6.5 Medium EPSS 1.3% KEV · Not listed
Description
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.

Remediation

Vendor Workaround

The vulnerability is most commonly associated with the "acl_xattr" module and can be mitigated by setting: ~~~ "acl_xattr:ignore system acls = no" ~~~

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-3792-1 samba security update
Debian DSA Debian DSA DSA-5525-1 samba security update
Debian DSA Debian DSA DSA-5647-1 samba security update
EUVD EUVD EUVD-2023-53981 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.
Ubuntu USN Ubuntu USN USN-6425-1 Samba vulnerabilities
Ubuntu USN Ubuntu USN USN-6425-3 Samba vulnerabilities
History
Type Values Removed Values Added
First Time appeared Redhat rhel Els
CPEs cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:rhel_els:6
cpe:/o:redhat:rhel_els:7
Vendors & Products Redhat rhel Els
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Metrics epss

{'score': 0.00476}

epss

{'score': 0.00409}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 7, 2026, 1:41 PM
Reserved
Aug 2, 2023, 9:43 AM
Status
Modified
Published
Nov 3, 2023, 8:15 AM
Modified
Nov 7, 2026, 2:16 PM
Severity
Moderate
Public date
Oct 10, 2023, 12:00 AM