Samba: access control bypass via vfs_ceph_rgw case-insensitive open
Summary
| CVE | CVE-2026-109411 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-28 20:17:17 UTC |
| Updated | 2026-10-30 05:16:58 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 8.1 HIGH from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
EPSS: 0.006490000 probability, percentile 0.510310000 (date 2026-10-29)
Problem Types: CWE-178 | CWE-178 Improper Handling of Case Sensitivity
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 8.1 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N |
| 3.1 | CNA | CVSS | 8.1 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Samba | Samba | affected 4.25.0 4.25.1 semver | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 10 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 6 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 6 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 7 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 8 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 9 | Not specified | Not specified |
| CNA | Red Hat | Red Hat OpenShift Container Platform 4 | Not specified | Not specified |
| CNA | Red Hat | Red Hat OpenShift Container Platform 4 | Not specified | Not specified |
| CNA | Red Hat | Red Hat OpenShift Container Platform 5 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| attachments.samba.org/attachment.cgi | [email protected] | attachments.samba.org | |
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | |
| attachments.samba.org/attachment.cgi | [email protected] | attachments.samba.org | |
| bugzilla.samba.org/show_bug.cgi | [email protected] | bugzilla.samba.org | |
| access.redhat.com/security/cve/CVE-2026-109411 | [email protected] | access.redhat.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank hataehoon for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-10-14T00:00:00.000Z | Reported to Red Hat. |
| CNA | 2026-10-23T15:00:00.000Z | Made public. |
Workarounds
CNA: 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.