CVE-2023-4091

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.

The vulnerability primarily affects Samba configurations using the "acl_xattr" module with the "acl_xattr:ignore system acls = yes" setting.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

The vulnerability is most commonly associated with the "acl_xattr" module and can be mitigated by setting:

"acl_xattr:ignore system acls = no"