{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2025-21836",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2024-12-29T08:45:45.777Z",
        "datePublished": "2025-03-07T09:09:56.127Z",
        "dateUpdated": "2026-08-05T11:54:49.695Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-05T11:54:49.695Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/kbuf: reallocate buf lists on upgrade\n\nIORING_REGISTER_PBUF_RING can reuse an old struct io_buffer_list if it\nwas created for legacy selected buffer and has been emptied. It violates\nthe requirement that most of the field should stay stable after publish.\nAlways reallocate it instead."
                }
            ],
            "metrics": [
                {
                    "cvssV3_1": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                        "baseScore": 7.8,
                        "baseSeverity": "HIGH"
                    },
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "AV:L - The vulnerable code is reached only through the io_uring_setup/io_uring_register syscalls; there is no network or adjacent path, so exploitation requires local access to issue syscalls.\nAC:L - The attacker performs every step themselves (create a legacy buffer group, empty it, upgrade the same bgid via PBUF_RING, then mmap), controlling both sides of any race; the trigger is fully deterministic and reliable.\nPR:L - io_uring is available to unprivileged users by default (kernel.io_uring_disabled=0) and provided-buffer registration needs no capability, so only a basic local user account is required.\nUI:N - The entire sequence is driven by the attacking process; no action by any other user or victim is needed.\nS:U - The corruption is confined to the kernel's own security authority (standard local privilege escalation) and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - The type confusion / use-after-free of the io_buffer_list and the retained user mapping to freed kernel pages give the attacker read access to reallocated kernel memory, enabling arbitrary kernel information disclosure.\nI:H - The same UAF and shared-page primitive give write access to freed/reallocated kernel memory, exploitable for arbitrary kernel write and privilege escalation as demonstrated for this io_uring buffer-ring bug class.\nA:H - At minimum the type confusion and use-after-free corrupt kernel structures, causing an oops/panic and denial of service."
                        }
                    ]
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "io_uring/kbuf.c"
                    ],
                    "versions": [
                        {
                            "version": "2fcabce2d7d34f69a888146dab15b36a917f09d4",
                            "lessThan": "146a185f6c05ee263db715f860620606303c4633",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "2fcabce2d7d34f69a888146dab15b36a917f09d4",
                            "lessThan": "7d0dc28dae836caf7645fef62a10befc624dd17b",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "2fcabce2d7d34f69a888146dab15b36a917f09d4",
                            "lessThan": "2a5febbef40ce968e295a7aeaa5d5cbd9e3e5ad4",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "2fcabce2d7d34f69a888146dab15b36a917f09d4",
                            "lessThan": "8802766324e1f5d414a81ac43365c20142e85603",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                },
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "io_uring/kbuf.c"
                    ],
                    "versions": [
                        {
                            "version": "5.19",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "5.19",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.79",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.16",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.13.4",
                            "lessThanOrEqual": "6.13.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.14",
                            "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": "5.19",
                                    "versionEndExcluding": "6.6.79"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "5.19",
                                    "versionEndExcluding": "6.12.16"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "5.19",
                                    "versionEndExcluding": "6.13.4"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "5.19",
                                    "versionEndExcluding": "6.14"
                                }
                            ]
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/146a185f6c05ee263db715f860620606303c4633"
                },
                {
                    "url": "https://git.kernel.org/stable/c/7d0dc28dae836caf7645fef62a10befc624dd17b"
                },
                {
                    "url": "https://git.kernel.org/stable/c/2a5febbef40ce968e295a7aeaa5d5cbd9e3e5ad4"
                },
                {
                    "url": "https://git.kernel.org/stable/c/8802766324e1f5d414a81ac43365c20142e85603"
                },
                {
                    "url": "https://u1f383.github.io/slides/talks/2025_Hexacon-Deja_Vu_in_Linux_io_uring_Breaking_Memory_Sharing_Again_After_Generations_of_Fixes.pdf"
                }
            ],
            "title": "io_uring/kbuf: reallocate buf lists on upgrade",
            "x_generator": {
                "engine": "bippy-1.2.0"
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    }
}