{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2025-71159",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2026-01-13T15:30:19.665Z",
        "datePublished": "2026-01-23T15:23:57.824Z",
        "dateUpdated": "2026-08-05T12:12:25.188Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-05T12:12:25.188Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node()\n\nPreviously, btrfs_get_or_create_delayed_node() set the delayed_node's\nrefcount before acquiring the root->delayed_nodes lock.\nCommit e8513c012de7 (\"btrfs: implement ref_tracker for delayed_nodes\")\nmoved refcount_set inside the critical section, which means there is\nno longer a memory barrier between setting the refcount and setting\nbtrfs_inode->delayed_node.\n\nWithout that barrier, the stores to node->refs and\nbtrfs_inode->delayed_node may become visible out of order. Another\nthread can then read btrfs_inode->delayed_node and attempt to\nincrement a refcount that hasn't been set yet, leading to a\nrefcounting bug and a use-after-free warning.\n\nThe fix is to move refcount_set back to where it was to take\nadvantage of the implicit memory barrier provided by lock\nacquisition.\n\nBecause the allocations now happen outside of the lock's critical\nsection, they can use GFP_NOFS instead of GFP_ATOMIC."
                }
            ],
            "metrics": [
                {
                    "cvssV3_1": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                        "baseScore": 9.8,
                        "baseSeverity": "CRITICAL"
                    },
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "AV:N - A remote attacker can reach the path through a writable Btrfs-backed ksmbd guest share: SMB2 WRITE reaches ksmbd_vfs_write(), kernel_write(), and the Btrfs ordered-write completion path. This is a reasonable network-facing Btrfs deployment.\nAC:L - Concurrent writes create multiple ordered extents whose parallel end-I/O workers can race while publishing and acquiring the same delayed node. The attacker controls the workload and can repeatedly create both sides of the race.\nPR:N - Although ksmbd checks the session, writable tree connection, and file handle, a guest-writable share grants these without attacker credentials. No prior account, capability, or local privilege is therefore required in that deployment.\nUI:N - The attacker directly triggers the race with concurrent write requests; no separate victim action is required.\nS:U - The vulnerable Btrfs code and the resulting kernel memory corruption are within the same host-kernel security authority.\nC:H - The lost reference can leave a delayed-node pointer usable after its slab object is freed and reused. Exploitation of this kernel use-after-free can expose arbitrary kernel memory.\nI:H - Subsequent mutex, flag, counter, tree, and inode-item operations write through the stale pointer. Heap reuse and spraying can turn these writes into kernel memory corruption and potential code execution.\nA:H - The observed refcount failure raises a kernel warning, and use of the prematurely freed delayed node can cause an oops, panic, hang, or filesystem shutdown."
                        }
                    ]
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/btrfs/delayed-inode.c"
                    ],
                    "versions": [
                        {
                            "version": "e8513c012de75fd65e2df5499572bc6ef3f6e409",
                            "lessThan": "c8385851a5435f4006281828d428e5d0b0bbf8af",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e8513c012de75fd65e2df5499572bc6ef3f6e409",
                            "lessThan": "83f59076a1ae6f5c6845d6f7ed3a1a373d883684",
                            "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/btrfs/delayed-inode.c"
                    ],
                    "versions": [
                        {
                            "version": "6.18",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.18",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.6",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.19",
                            "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": "6.18",
                                    "versionEndExcluding": "6.18.6"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.18",
                                    "versionEndExcluding": "6.19"
                                }
                            ]
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/c8385851a5435f4006281828d428e5d0b0bbf8af"
                },
                {
                    "url": "https://git.kernel.org/stable/c/83f59076a1ae6f5c6845d6f7ed3a1a373d883684"
                }
            ],
            "title": "btrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node()",
            "x_generator": {
                "engine": "bippy-1.2.0"
            }
        }
    }
}