CVE-2026-109411

Samba: access control bypass via vfs_ceph_rgw case-insensitive open

Published Oct 28, 2026 CVSS 3.1 · 8.1 High EPSS < 1% KEV · Not listed
Description
An access control bypass flaw was identified in Samba's vfs_ceph_rgw module in it's openat() function. An authenticated user can bypass access controls to read or overwrite restricted files on shares configured with the experimental vfs_ceph_rgw module. When a client requests an existing file using mismatched character casing, the module fails to perform a case-insensitive lookup correctly, causing the server to treat the operation as creating a new file. As a result, the server skips standard permission checks on the existing file, allowing the attacker to access or overwrite sensitive data owned by other users.

Remediation

Vendor Workaround

Only shares configured with the vfs_ceph_rgw module are affected. To mitigate this vulnerability, disable the experimental `vfs_ceph_rgw` module on any configured Samba shares. Edit `/etc/samba/smb.conf` to remove `ceph_rgw` from the `vfs objects` setting under the relevant share sections, then reload the Samba service: ``` systemctl reload smb ``` Warning: Reloading or restarting the `smb` service may briefly interrupt active client sessions. Additionally, removing this module disables Ceph RGW integration for the affected shares. Setting ```case sensitive = yes``` on affected shares avoids the vulnerability, because the differently-cased name is then treated as a distinct object rather than resolving to the existing file. Note: This changes share behavior for clients that rely on case-insensitive name handling.

Tracking

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Advisories

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History
Type Values Removed Values Added
First Time appeared Redhat rhel Els
CPEs cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
cpe:/a:redhat:enterprise_linux:10
cpe:/a:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:9
cpe:/o:redhat:rhel_els:6
cpe:/o:redhat:rhel_els:7
Vendors & Products Redhat rhel Els
Type Values Removed Values Added
CPEs cpe:/a:redhat:openshift:5
Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
Description An access control bypass flaw was found in Samba's vfs_ceph_rgw module in it's openat() function. An authenticated user can bypass access controls to read or overwrite restricted files on shares configured with the experimental vfs_ceph_rgw module. When a client requests an existing file using mismatched character casing, the module fails to perform a case-insensitive lookup correctly, causing the server to treat the operation as creating a new file. As a result, the server skips standard permission checks on the existing file, allowing the attacker to access or overwrite sensitive data owned by other users. An access control bypass flaw was identified in Samba's vfs_ceph_rgw module in it's openat() function. An authenticated user can bypass access controls to read or overwrite restricted files on shares configured with the experimental vfs_ceph_rgw module. When a client requests an existing file using mismatched character casing, the module fails to perform a case-insensitive lookup correctly, causing the server to treat the operation as creating a new file. As a result, the server skips standard permission checks on the existing file, allowing the attacker to access or overwrite sensitive data owned by other users.
Type Values Removed Values Added
Title samba: Access control bypass via vfs_ceph_rgw case-insensitive open Samba: access control bypass via vfs_ceph_rgw case-insensitive open
First Time appeared Redhat
Redhat enterprise Linux
Redhat openshift
CPEs cpe:/a:redhat:openshift:4
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Redhat openshift
References
Type Values Removed Values Added
First Time appeared Samba
Samba samba
Vendors & Products Samba
Samba samba
Type Values Removed Values Added
Description An access control bypass flaw was found in Samba's vfs_ceph_rgw module in it's openat() function. An authenticated user can bypass access controls to read or overwrite restricted files on shares configured with the experimental vfs_ceph_rgw module. When a client requests an existing file using mismatched character casing, the module fails to perform a case-insensitive lookup correctly, causing the server to treat the operation as creating a new file. As a result, the server skips standard permission checks on the existing file, allowing the attacker to access or overwrite sensitive data owned by other users.
Title samba: Access control bypass via vfs_ceph_rgw case-insensitive open
Weaknesses CWE-178
References
Metrics threat_severity

None

cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N'}

threat_severity

Important

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 4, 2026, 9:48 PM
Reserved
Oct 12, 2026, 3:19 PM
Status
Awaiting Analysis
Published
Oct 28, 2026, 8:17 PM
Modified
Nov 4, 2026, 10:17 PM
Severity
Important
Public date
Oct 23, 2026, 3:00 PM