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{"acknowledgement": "Red Hat would like to thank hataehoon for reporting this issue.", "bugzilla": {"description": "samba: Access control bypass via vfs_ceph_rgw case-insensitive open", "id": "2552136", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2552136"}, "csaw": false, "cvss3": {"cvss3_base_score": "8.1", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N", "status": "draft"}, "cwe": "CWE-178", "details": ["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."], "mitigation": {"lang": "en:us", "value": "Only shares configured with the vfs_ceph_rgw module are affected.\nTo 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:\n```\nsystemctl reload smb\n```\nWarning: Reloading or restarting the `smb` service may briefly interrupt active client sessions. Additionally, removing this module disables Ceph RGW integration for the affected shares.\nSetting ```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. \nNote: This changes share behavior for clients that rely on case-insensitive name handling."}, "name": "CVE-2026-109411", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "samba", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "samba", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "samba4", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "samba", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "samba", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "samba", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "openshift/ose-rhel-coreos-8", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "openshift/ose-rhel-coreos-9", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-10-23T15:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-109411\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-109411\nhttps://attachments.samba.org/attachment.cgi?id=19294\nhttps://attachments.samba.org/attachment.cgi?id=19295\nhttps://bugzilla.samba.org/show_bug.cgi?id=16276"], "statement": "This vulnerability is strictly limited to Samba deployments utilizing the experimental S3-to-SMB gateway feature (vfs_ceph_rgw).\nThis specific feature was introduced in upstream Samba version 4.25.\nStandard Red Hat Enterprise Linux (RHEL), Red Hat Ceph Storage, Red Hat In-Vehicle OS (RHIVOS), and OpenShift Container Platform packages do not include or support this experimental module. The Samba versions shipped by Red Hat predate the introduction of this feature; therefore, the vulnerable code is not present.\n**Clarification for Red Hat Ceph Storage Users:**\nPlease distinguish between the standard CephFS integration and the vulnerable component:\n**Safe (vfs_ceph):** Red Hat Ceph Storage utilizes the native vfs_ceph module for CephFS integration. This module interacts directly with libcephfs to enforce standard POSIX ACLs. It is architecturally distinct and is not related to this issue.\n**Vulnerable (vfs_ceph_rgw):** The vulnerability exists solely in this separate, experimental vfs_ceph_rgw module (used for mapping S3 buckets to SMB) and as said above, this module is not present in Red Hat distributed Samba packages.", "threat_severity": "Important"}