CVE-2025-40039

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However, the locking implementation was\nflawed, leading to potential race conditions.\n\nIn ksmbd_session_rpc_open(), the code incorrectly acquired only a read lock\nbefore calling xa_store() and xa_erase(). Since these operations modify\nthe XArray structure, a write lock is required to ensure exclusive access\nand prevent data corruption from concurrent modifications.\n\nFurthermore, ksmbd_session_rpc_method() accessed the list using xa_load()\nwithout holding any lock at all. This could lead to reading inconsistent\ndata or a potential use-after-free if an entry is concurrently removed and\nthe pointer is dereferenced.\n\nFix these issues by:\n1. Using down_write() and up_write() in ksmbd_session_rpc_open()\n to ensure exclusive access during XArray modification, and ensuring\n the lock is correctly released on error paths.\n2. Adding down_read() and up_read() in ksmbd_session_rpc_method()\n to safely protect the lookup."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:N - The vulnerable code is in ksmbd, the in-kernel SMB server, and is driven entirely by SMB2 requests (CREATE/CLOSE/IOCTL/READ/WRITE/QUERY_INFO) arriving over TCP port 445 from a remote peer. No local access is needed.\nAC:L - The attacker controls both sides of the race: the pipe handle is an attacker-chosen VolatileFileId, and ksmbd_queue_work() executes each SMB2 request on a separate ksmbd-io worker (plus SMB3 multichannel), so concurrent SMB2_CLOSE and SMB2_IOCTL/READ/WRITE requests run in parallel with unlimited retries.\nPR:L - Reaching create_smb2_pipe() requires a session in SMB2_SESSION_VALID state (ksmbd_session_lookup_all() rejects IN_PROGRESS) plus a tree connect to IPC$, i.e. any valid low-privileged SMB account; no administrative rights are needed, and with guest mapping enabled even credentials are unnecessary.\nUI:N - The entire sequence is performed by the attacker's own SMB client against the server; no action by any local user or administrator is required.\nS:U - The use-after-free corrupts kernel heap state within the same kernel security authority; no hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - The unlocked xa_load() dereferences a kfree()'d struct ksmbd_session_rpc, disclosing reused kernel heap contents as the RPC method flags; a UAF of this kind gives control over freed-object contents and can be leveraged into arbitrary kernel memory disclosure, and the resulting flags can steer the root ksmbd.mountd daemon into SAMR/LSARPC handlers the client never opened.\nI:H - The stale entry->method value read from a reused 8-byte slab object is heap-groomable by the attacker and directly selects which privileged RPC method the root-privileged userspace daemon executes with client-supplied payload; use-after-free conditions are generally leverageable into arbitrary-write and control-flow hijack primitives.\nA:H - Dereferencing the freed entry after the slab object or page has been released oopses the ksmbd worker thread, and the unsynchronized RPC handle teardown corrupts session state, yielding a repeatable remote kernel crash / denial of service."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/server/mgmt/user_session.c"], "versions": [{"version": "a4348710a7267705b75692dc1a000920481d1d92", "lessThan": "69674b029002b1d90b655f014bdf64f404efa54d", "status": "affected", "versionType": "git"}, {"version": "b685757c7b08d5073046fb379be965fd6c06aafc", "lessThan": "6b615a8fb3af0baf8126cde3d4fee97d57222ffc", "status": "affected", "versionType": "git"}, {"version": "b685757c7b08d5073046fb379be965fd6c06aafc", "lessThan": "5cc679ba0f4505936124cd4179ba66bb0a4bd9f3", "status": "affected", "versionType": "git"}, {"version": "b685757c7b08d5073046fb379be965fd6c06aafc", "lessThan": "6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1", "status": "affected", "versionType": "git"}, {"version": "b685757c7b08d5073046fb379be965fd6c06aafc", "lessThan": "305853cce379407090a73b38c5de5ba748893aee", "status": "affected", "versionType": "git"}, {"version": "1f485b54d04a920723984062c912174330a05178", "status": "affected", "versionType": "git"}, {"version": "052b41ef2abe274f068e892aee81406f11bd1f3a", "status": "affected", "versionType": "git"}, {"version": "5.15.145", "lessThan": "5.16", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/server/mgmt/user_session.c"], "versions": [{"version": "6.3", "status": "affected"}, {"version": "0", "lessThan": "6.3", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.123", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.53", "lessThanOrEqual": "6.12.*", "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": "6.3", "versionEndExcluding": "6.6.123"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "6.12.53"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "6.17.3"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "6.18"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.145"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/69674b029002b1d90b655f014bdf64f404efa54d"}, {"url": "https://git.kernel.org/stable/c/6b615a8fb3af0baf8126cde3d4fee97d57222ffc"}, {"url": "https://git.kernel.org/stable/c/5cc679ba0f4505936124cd4179ba66bb0a4bd9f3"}, {"url": "https://git.kernel.org/stable/c/6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1"}, {"url": "https://git.kernel.org/stable/c/305853cce379407090a73b38c5de5ba748893aee"}], "title": "ksmbd: Fix race condition in RPC handle list access", "x_generator": {"engine": "bippy-1.2.0"}}}}

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Access to this list is intended to be protected by\n'sess->rpc_lock' (an rw_semaphore). However, the locking implementation was\nflawed, leading to potential race conditions.\n\nIn ksmbd_session_rpc_open(), the code incorrectly acquired only a read lock\nbefore calling xa_store() and xa_erase(). Since these operations modify\nthe XArray structure, a write lock is required to ensure exclusive access\nand prevent data corruption from concurrent modifications.\n\nFurthermore, ksmbd_session_rpc_method() accessed the list using xa_load()\nwithout holding any lock at all. This could lead to reading inconsistent\ndata or a potential use-after-free if an entry is concurrently removed and\nthe pointer is dereferenced.\n\nFix these issues by:\n1. Using down_write() and up_write() in ksmbd_session_rpc_open()\n to ensure exclusive access during XArray modification, and ensuring\n the lock is correctly released on error paths.\n2. Adding down_read() and up_read() in ksmbd_session_rpc_method()\n to safely protect the lookup."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nksmbd: Soluci\u00f3n de condici\u00f3n de carrera en el acceso a la lista de manejadores RPC\n\nEl XArray 'sess->rpc_handle_list' gestiona los manejadores RPC dentro de una sesi\u00f3n ksmbd. El acceso a esta lista est\u00e1 destinado a ser protegido por 'sess->rpc_lock' (un rw_semaphore). Sin embargo, la implementaci\u00f3n del bloqueo era defectuosa, lo que llevaba a potenciales condiciones de carrera.\n\nEn ksmbd_session_rpc_open(), el c\u00f3digo adquiri\u00f3 incorrectamente solo un bloqueo de lectura antes de llamar a xa_store() y xa_erase(). Dado que estas operaciones modifican la estructura del XArray, se requiere un bloqueo de escritura para asegurar el acceso exclusivo y prevenir la corrupci\u00f3n de datos por modificaciones concurrentes.\n\nAdem\u00e1s, ksmbd_session_rpc_method() accedi\u00f3 a la lista usando xa_load() sin mantener ning\u00fan bloqueo en absoluto. Esto podr\u00eda llevar a la lectura de datos inconsistentes o a un potencial uso despu\u00e9s de liberaci\u00f3n si una entrada es eliminada concurrentemente y el puntero es desreferenciado.\n\nSe solucionan estos problemas de la siguiente manera:\n1. Usando down_write() y up_write() en ksmbd_session_rpc_open() para asegurar el acceso exclusivo durante la modificaci\u00f3n del XArray, y asegurando que el bloqueo se libere correctamente en las rutas de error.\n2. A\u00f1adiendo down_read() y up_read() en ksmbd_session_rpc_method() para proteger de forma segura la b\u00fasqueda."}], "id": "CVE-2025-40039", "lastModified": "2026-10-19T21:10:00.160", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 8.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}, {"cvssData": {"attackComplexity": "HIGH", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 4.7, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.0, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2025-10-28T12:15:37.847", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/305853cce379407090a73b38c5de5ba748893aee"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5cc679ba0f4505936124cd4179ba66bb0a4bd9f3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/69674b029002b1d90b655f014bdf64f404efa54d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6b615a8fb3af0baf8126cde3d4fee97d57222ffc"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6bd7e0e55dcea2cf0d391bbc21c2eb069b4be3e1"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-362"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: ksmbd: Fix race condition in RPC handle list access", "id": "2406744", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2406744"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "details": ["No description is available for this CVE."], "name": "CVE-2025-40039", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not 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": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-10-28T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-40039\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-40039\nhttps://lore.kernel.org/linux-cve-announce/2025102812-CVE-2025-40039-2d65@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-10-29T10:58:14.187394+00:00", "updated": "2025-10-29T10:58:14.187419+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}