High · CVSS 8.1CVE-2026-109411

Samba: access control bypass via vfs_ceph_rgw case-insensitive openCVE-2026-109411

Answer in brief

CVE-2026-109411 records a High severity (CVSS 8.1) vulnerability in Samba: access control bypass via vfs_ceph_rgw case-insensitive open. The current sources do not mark it as known exploited. The current feed maps Samba/samba (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 28, 2026Updated Oct 28, 2026Source checked Oct 28, 2026First seen by HOL Oct 28, 2026Material review Oct 28, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.1
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Samba/samba (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Samba/sambageneric	>=4.25.0 <4.25.1	4.25.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for Samba/samba.
Review the reported fix. Source-reported 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.

Evidence timeline and material changes

Published upstream
Oct 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 28, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.

Package

Affected range

Fixed version

Samba/sambageneric

>=4.25.0 <4.25.1

4.25.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for Samba/samba.

Review the reported fix. Source-reported 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.

Sources and claim methodology

Upstream source description

Quoted source text, attributed separately from HOL analysis.