---
id: "CVE-2026-109411"
kind: "vulnerability"
aliases: ["CVE-2026-109411"]
title: "Samba: case mismatch in vfs_ceph_rgw lets users overwrite restricted files"
severity: "high"
cvss: 8.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["ceph", "file-shares", "package", "samba", "self-hosted"]
not_affected_if: ["default-config", "no-vfs-ceph-rgw"]
published_at: "2026-10-28T20:17:17+00:00"
first_seen_at: "2026-10-28T20:35:10+00:00"
updated_at: "2026-10-28T20:36:10+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-109411", "first_seen_at": "2026-10-28T20:35:10+00:00"}]
---

# Samba: case mismatch in vfs_ceph_rgw lets users overwrite restricted files

Samba's experimental vfs_ceph_rgw module mishandles file lookups when the client uses different letter casing, so the server treats an existing file as a new one and skips its permission checks. An authenticated user can read or overwrite files owned by other users on affected shares.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check whether the share configuration loads the module with `testparm -s | grep -i vfs_ceph_rgw` or by searching smb.conf for `vfs objects` containing `ceph_rgw`.
- Check the installed version with `smbd --version`; the sources do not list the fixed versions.

## Fix

- Remove `ceph_rgw` from `vfs objects` on affected shares or stop using the module until a patched Samba release is installed.
- Upgrade Samba to a patched release; the fixed version is unknown from the sources.

## Timeline

- 2026-10-28T20:35:10+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-109411

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_