CVE-2026-31539

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The ksmbd server path processes the affected negotiation and data-transfer credit handling from network-originated RDMA messages.\nAC:L - The issue is a receive-credit accounting race, but the remote peer can repeatedly drive both message arrival and credit-request/response behavior with crafted SMBDirect traffic. No unusual victim state or uncontrollable condition is required beyond an enabled SMBDirect RDMA deployment.\nPR:N - The server-side path accepts the RDMA connection and performs SMBDirect negotiation and data-transfer credit handling before SMB session authentication. A remote peer does not need SMB credentials to reach the vulnerable credit logic.\nUI:N - Exploitation against the server path requires only network/RDMA traffic from the attacker. No local user or administrator action is needed after the service is exposed.\nS:U - The impact remains within the kernel SMBDirect/SMB service security authority. There is no VM escape, IOMMU bypass, or cross-authority boundary crossing.\nC:N - The bug overgrants receive credits but does not expose a kernel read primitive; incoming payload bounds are checked before reassembly. An RDMA send without a posted receive should produce transport/RNR failure rather than disclose memory.\nI:N - The investigation did not identify an arbitrary write or memory-corruption primitive. The false credit causes receive-queue/transport state inconsistency, not attacker-controlled modification of kernel data.\nA:H - False credits can allow the peer to send when no real receive buffer is posted, causing RDMA QP/transport errors and SMBDirect disconnects with RNR retries disabled. Because this is remotely and unauthenticatedly repeatable against the exposed SMBDirect service, availability impact is high."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/common/smbdirect/smbdirect_socket.h"], "versions": [{"version": "5fb9b459b3686e366640edd4e62805ef7b4de927", "lessThan": "e811e60e1cc79923c4388146eb1fa26a7482731e", "status": "affected", "versionType": "git"}, {"version": "5fb9b459b3686e366640edd4e62805ef7b4de927", "lessThan": "f99996870222b598914a1f49d7375dc23752c237", "status": "affected", "versionType": "git"}, {"version": "5fb9b459b3686e366640edd4e62805ef7b4de927", "lessThan": "6e3c5052f9686192e178806e017b7377155f4bab", "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/common/smbdirect/smbdirect_socket.h"], "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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/e811e60e1cc79923c4388146eb1fa26a7482731e"}, {"url": "https://git.kernel.org/stable/c/f99996870222b598914a1f49d7375dc23752c237"}, {"url": "https://git.kernel.org/stable/c/6e3c5052f9686192e178806e017b7377155f4bab"}], "title": "smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-31539", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-10-16T15:10:46.426998Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-362", "description": "CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"}]}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-19T18:55:58.491Z"}}]}}

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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: smbdirect: introduce 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."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nsmb: smbdirect: se introduce smbdirect_socket.recv_io.credits.available\n\nLa l\u00f3gica de gestionar los cr\u00e9ditos recv contando los recv_io publicados y los cr\u00e9ditos concedidos es propensa a condiciones de carrera.\n\nEsto se debe a que el par ya podr\u00eda haber consumido un cr\u00e9dito, pero entre la recepci\u00f3n del recv entrante en el hardware y el procesamiento de la finalizaci\u00f3n en las funciones \u2019recv_done\u2019 es probable que tengamos una ventana donde concedemos cr\u00e9ditos que en realidad no existen.\n\nAs\u00ed que es mejor tener un contador dedicado para los cr\u00e9ditos disponibles, el cual ser\u00e1 incrementado cuando publiquemos nuevos b\u00faferes recv y disminuido cuando concedamos los cr\u00e9ditos al par."}], "id": "CVE-2026-31539", "lastModified": "2026-11-11T23:10:00.263", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": 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"vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-362"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available", "id": "2461575", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2461575"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-821", "details": ["A flaw was found in the Linux kernel's `smbdirect` module. A race condition in the receive credit management logic allows the system to grant credits that a peer has already consumed. This timing vulnerability, occurring during the processing of incoming data, could lead to resource exhaustion and potentially result in a denial of service (DoS) condition."], "name": "CVE-2026-31539", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-04-24T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-31539\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31539\nhttps://lore.kernel.org/linux-cve-announce/2026042434-CVE-2026-31539-fe1a@gregkh/T"], "threat_severity": "Moderate"}

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