UBUNTU-CVE-2026-109411

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UBUNTU-CVE-2026-109411

Summary:

Details: 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.

References: https://ubuntu.com/security/CVE-2026-109411, https://www.cve.org/CVERecord?id=CVE-2026-109411, https://bugzilla.samba.org/show_bug.cgi?id=16276