{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2025-40072",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2025-04-16T07:20:57.160Z",
        "datePublished": "2025-10-28T11:48:39.999Z",
        "dateUpdated": "2026-05-11T21:41:56.450Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-05-11T21:41:56.450Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing\n\nThe function do_fanotify_mark() does not validate if\nmnt_ns_from_dentry() returns NULL before dereferencing mntns->user_ns.\nThis causes a NULL pointer dereference in do_fanotify_mark() if the\npath is not a mount namespace object.\n\nFix this by checking mnt_ns_from_dentry()'s return value before\ndereferencing it.\n\nBefore the patch\n\n$ gcc fanotify_nullptr.c -o fanotify_nullptr\n$ mkdir A\n$ ./fanotify_nullptr\nFanotify fd: 3\nfanotify_mark: Operation not permitted\n$ unshare -Urm\nFanotify fd: 3\nKilled\n\nint main(void){\n    int ffd;\n    ffd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_MNT, 0);\n    if(ffd < 0){\n        perror(\"fanotify_init\");\n        exit(EXIT_FAILURE);\n    }\n\n    printf(\"Fanotify fd: %d\\n\",ffd);\n\n    if(fanotify_mark(ffd, FAN_MARK_ADD | FAN_MARK_MNTNS,\nFAN_MNT_ATTACH, AT_FDCWD, \"A\") < 0){\n        perror(\"fanotify_mark\");\n        exit(EXIT_FAILURE);\n    }\n\nreturn 0;\n}\n\nAfter the patch\n\n$ gcc fanotify_nullptr.c -o fanotify_nullptr\n$ mkdir A\n$ ./fanotify_nullptr\nFanotify fd: 3\nfanotify_mark: Operation not permitted\n$ unshare -Urm\nFanotify fd: 3\nfanotify_mark: Invalid argument\n\n[   25.694973] BUG: kernel NULL pointer dereference, address: 0000000000000038\n[   25.695006] #PF: supervisor read access in kernel mode\n[   25.695012] #PF: error_code(0x0000) - not-present page\n[   25.695017] PGD 109a30067 P4D 109a30067 PUD 142b46067 PMD 0\n[   25.695025] Oops: Oops: 0000 [#1] SMP NOPTI\n[   25.695032] CPU: 4 UID: 1000 PID: 1478 Comm: fanotify_nullpt Not\ntainted 6.17.0-rc4 #1 PREEMPT(lazy)\n[   25.695040] Hardware name: VMware, Inc. VMware Virtual\nPlatform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020\n[   25.695049] RIP: 0010:do_fanotify_mark+0x817/0x950\n[   25.695066] Code: 04 00 00 e9 45 fd ff ff 48 8b 7c 24 48 4c 89 54\n24 18 4c 89 5c 24 10 4c 89 0c 24 e8 b3 11 fc ff 4c 8b 54 24 18 4c 8b\n5c 24 10 <48> 8b 78 38 4c 8b 0c 24 49 89 c4 e9 13 fd ff ff 8b 4c 24 28\n85 c9\n[   25.695081] RSP: 0018:ffffd31c469e3c08 EFLAGS: 00010203\n[   25.695104] RAX: 0000000000000000 RBX: 0000000001000000 RCX: ffff8eb48aebd220\n[   25.695110] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8eb4835e8180\n[   25.695115] RBP: 0000000000000111 R08: 0000000000000000 R09: 0000000000000000\n[   25.695142] R10: ffff8eb48a7d56c0 R11: ffff8eb482bede00 R12: 00000000004012a7\n[   25.695148] R13: 0000000000000110 R14: 0000000000000001 R15: ffff8eb48a7d56c0\n[   25.695154] FS:  00007f8733bda740(0000) GS:ffff8eb61ce5f000(0000)\nknlGS:0000000000000000\n[   25.695162] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   25.695170] CR2: 0000000000000038 CR3: 0000000136994006 CR4: 00000000003706f0\n[   25.695201] Call Trace:\n[   25.695209]  <TASK>\n[   25.695215]  __x64_sys_fanotify_mark+0x1f/0x30\n[   25.695222]  do_syscall_64+0x82/0x2c0\n..."
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/notify/fanotify/fanotify_user.c"
                    ],
                    "versions": [
                        {
                            "version": "58f5fbeb367ff6f30a2448b2cad70f70b2de4b06",
                            "lessThan": "73ce2a774ad6497cbd48dc4f8a5d699bc417f3fa",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "58f5fbeb367ff6f30a2448b2cad70f70b2de4b06",
                            "lessThan": "62e59ffe8787b5550ccff70c30b6f6be6a3ac3dd",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                },
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/notify/fanotify/fanotify_user.c"
                    ],
                    "versions": [
                        {
                            "version": "6.16",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.16",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.17.3",
                            "lessThanOrEqual": "6.17.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }
            ],
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "operator": "OR",
                            "negate": false,
                            "cpeMatch": [
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.16",
                                    "versionEndExcluding": "6.17.3"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.16",
                                    "versionEndExcluding": "6.18"
                                }
                            ]
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/73ce2a774ad6497cbd48dc4f8a5d699bc417f3fa"
                },
                {
                    "url": "https://git.kernel.org/stable/c/62e59ffe8787b5550ccff70c30b6f6be6a3ac3dd"
                }
            ],
            "title": "fanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing",
            "x_generator": {
                "engine": "bippy-1.2.0"
            }
        }
    }
}