CVE-2026-52944

ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE

cve-program · severity unknownCVSS unknownCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-52944

Published

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE FSCTL_SET_SPARSE in fsctl_set_sparse() modifies the file's sparse attribute and saves it through xattr without any permission checks. This exposes two issues: 1) A client on a read-only share can change the sparse attribute on files it opened, even though the share is read-only. Other FSCTL write operations already check test_tree_conn_flag(work->tcon, KSMBD_TREE_CONN_FLAG_WRITABLE), but FSCTL_SET_SPARSE does not. 2) Even on writable shares, clients without FILE_WRITE_DATA or FILE_WRITE_ATTRIBUTES access should not modify the sparse attribute. Similar handle-level checks exist in other functions but are missing here. Add both share-level writable check and per-handle access check. Use goto out on error to avoid leaking file references.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-52944

Published

Linux

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/smb/server/smb2pdu.c"
                    ],
                    "versions": [
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "ef664475c1bf1a27d45dae6848ca9c9c4d86853f",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "3a9a0a1c38ef90788f5d7c4b29903c8b220f744a",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "3127a884525dc8ca4def73254bfcd3ccef0bf812",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "c5ab11263e3c89aa7989afc5374ef7743e092fd0",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "de9eb0b44fa9123170e6245b49638e0e453c10f8",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "aef151bcfa494bfe983669de2726734b534adb73",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "cc57232cae23c0df91b4a59d0f519141ce9b5b02",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

Linux

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/smb/server/smb2pdu.c"
                    ],
                    "versions": [
                        {
                            "version": "5.15",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "5.15",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.15.221",
                            "lessThanOrEqual": "5.15.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.188",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.143",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.110",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.35",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.0.12",
                            "lessThanOrEqual": "7.0.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.1",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON