{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-31538",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2026-03-09T15:48:24.113Z",
        "datePublished": "2026-04-24T14:30:25.598Z",
        "dateUpdated": "2026-08-05T12:23:22.947Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-05T12:23:22.947Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: server: make use of smbdirect_socket.recv_io.credits.available\n\nThe logic off managing recv credits by counting posted recv_io and\ngranted credits is racy.\n\nThat's because the peer might already consumed a credit,\nbut between receiving the incoming recv at the hardware\nand processing the completion in the 'recv_done' functions\nwe likely have a window where we grant credits, which\ndon't really exist.\n\nSo we better have a decicated counter for the\navailable credits, which will be incremented\nwhen we posted new recv buffers and drained when\nwe grant the credits to the peer.\n\nThis fixes regression Namjae reported with\nthe 6.18 release."
                }
            ],
            "metrics": [
                {
                    "cvssV3_1": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
                        "baseScore": 7.5,
                        "baseSeverity": "HIGH"
                    },
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "AV:N - SMB Direct is a network-facing ksmbd RDMA transport listening on SMB/RDMA ports, and the vulnerable credit path is reached by packets from a remote SMB Direct peer. The attacker only needs network access to the exposed SMB Direct service.\nAC:L - The race is between receive completion processing and server credit grants, but the attacker controls the RDMA connection traffic and can repeatedly pipeline/flood requests to hit the window. No unusual victim-side condition is required beyond SMB Direct being enabled.\nPR:N - The affected path is in SMB Direct transport negotiation and data transfer handling before SMB session authentication is required. A remote unauthenticated peer can reach the credit accounting logic.\nUI:N - No victim user action is needed after the ksmbd SMB Direct service is running. The attacker triggers the issue by connecting and sending SMB Direct traffic.\nS:U - The impact remains within the kernel ksmbd/SMB Direct service security authority. There is no VM escape, sandbox escape, or cross-scope boundary change.\nC:N - The bug is receive-credit accounting, not an out-of-bounds access, use-after-free, or disclosure path. It does not provide a defensible kernel memory read primitive.\nI:N - Over-granting receive credits does not grant authorization or create a write primitive into kernel memory. The RDMA receive path consumes posted receive buffers and fails/disconnects when credits are invalid rather than allowing attacker-controlled memory modification.\nA:H - The peer can be granted credits for receive buffers that no longer exist, leading to RDMA receive-not-ready/QP errors or disconnects. Because this can be triggered remotely and repeatedly without authentication, it can deny SMB Direct service availability."
                        }
                    ]
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/smb/server/transport_rdma.c"
                    ],
                    "versions": [
                        {
                            "version": "89b021a72663c4d96d8a8b85272bb42d991a1c6f",
                            "lessThan": "66c082e3d4651e8629a393a9e182b01eb50fb0a3",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "89b021a72663c4d96d8a8b85272bb42d991a1c6f",
                            "lessThan": "809cbd31aa4f87a1b889532244c9cf30eb022385",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "89b021a72663c4d96d8a8b85272bb42d991a1c6f",
                            "lessThan": "26ad87a2cfb8c1384620d1693a166ed87303046e",
                            "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/smb/server/transport_rdma.c"
                    ],
                    "versions": [
                        {
                            "version": "6.18",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.18",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.11",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.19.1",
                            "lessThanOrEqual": "6.19.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.0",
                            "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": "6.18.11"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.18",
                                    "versionEndExcluding": "6.19.1"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.18",
                                    "versionEndExcluding": "7.0"
                                }
                            ]
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                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/66c082e3d4651e8629a393a9e182b01eb50fb0a3"
                },
                {
                    "url": "https://git.kernel.org/stable/c/809cbd31aa4f87a1b889532244c9cf30eb022385"
                },
                {
                    "url": "https://git.kernel.org/stable/c/26ad87a2cfb8c1384620d1693a166ed87303046e"
                }
            ],
            "title": "smb: server: make use of smbdirect_socket.recv_io.credits.available",
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}