Samba SMB Truncation via acl_xattr despite Read-Only
CVE-2023-4091 Published on November 3, 2023

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

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Vulnerability Analysis

CVE-2023-4091 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, a high impact on integrity, and no impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
HIGH
Availability Impact:
NONE

Timeline

Reported to Red Hat.

Made public. 7 days later.

Weakness Type

Incorrect Default Permissions

During installation, installed file permissions are set to allow anyone to modify those files.


Products Associated with CVE-2023-4091

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2023-4091 are published in these products:

Canonical Ubuntu Linux
 
Samba
 
Fedora Project Fedora
 
Red Hat Enterprise Linux (RHEL)
 
Red Hat Storage
 
Red Hat Enterprise Linux Eus
 
Oracle
 
Red Hat Rhel Eus
 
Red Hat Rhev Hypervisor
 

Affected Versions

Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8.6 Extended Update Support: Red Hat Enterprise Linux 8.8 Extended Update Support: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9.0 Extended Update Support: Red Hat Enterprise Linux 9.2 Extended Update Support: Red Hat Virtualization 4 for Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 7: Red Hat Storage 3:

Exploit Probability

EPSS
0.48%
Percentile
64.52%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.