CVE-2025-37871

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2025-37871", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T04:51:23.959Z", "datePublished": "2025-05-09T06:43:59.720Z", "dateUpdated": "2026-08-05T11:57:57.052Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:57:57.052Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: decrease sc_count directly if fail to queue dl_recall\n\nA deadlock warning occurred when invoking nfs4_put_stid following a failed\ndl_recall queue operation:\n T1 T2\n nfs4_laundromat\n nfs4_get_client_reaplist\n nfs4_anylock_blockers\n__break_lease\n spin_lock // ctx->flc_lock\n spin_lock // clp->cl_lock\n nfs4_lockowner_has_blockers\n locks_owner_has_blockers\n spin_lock // flctx->flc_lock\n nfsd_break_deleg_cb\n nfsd_break_one_deleg\n nfs4_put_stid\n refcount_dec_and_lock\n spin_lock // clp->cl_lock\n\nWhen a file is opened, an nfs4_delegation is allocated with sc_count\ninitialized to 1, and the file_lease holds a reference to the delegation.\nThe file_lease is then associated with the file through kernel_setlease.\n\nThe disassociation is performed in nfsd4_delegreturn via the following\ncall chain:\nnfsd4_delegreturn --> destroy_delegation --> destroy_unhashed_deleg -->\nnfs4_unlock_deleg_lease --> kernel_setlease --> generic_delete_lease\nThe corresponding sc_count reference will be released after this\ndisassociation.\n\nSince nfsd_break_one_deleg executes while holding the flc_lock, the\ndisassociation process becomes blocked when attempting to acquire flc_lock\nin generic_delete_lease. This means:\n1) sc_count in nfsd_break_one_deleg will not be decremented to 0;\n2) The nfs4_put_stid called by nfsd_break_one_deleg will not attempt to\nacquire cl_lock;\n3) Consequently, no deadlock condition is created.\n\nGiven that sc_count in nfsd_break_one_deleg remains non-zero, we can\nsafely perform refcount_dec on sc_count directly. This approach\neffectively avoids triggering deadlock warnings."}], "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 - The bug is in the in-kernel NFS server's delegation-recall path (fs/nfsd/nfs4state.c, nfsd_break_one_deleg), which is driven entirely by remote NFSv4 protocol operations \u2014 a remote client obtains a delegation via OPEN, and a second remote client's conflicting OPEN drives __break_lease() into nfsd_break_deleg_cb(). No local access to the server is required.\nAC:L - The attacker reaches the faulty !queued branch at will: __break_lease() only sets FL_UNLOCK_PENDING for write-breaks, so a read-conflicting OPEN followed immediately by a write-conflicting OPEN calls lm_break() twice on the same lease, and the second nfsd4_run_cb() finds cb_work still pending so queue_work() returns false. Both sides are attacker-driven and the sequence can be retried indefinitely; the affected stable branches have no NFSD4_CALLBACK_RUNNING guard at all.\nPR:N - Reaching the code only requires being an NFSv4 client of an export; with the default AUTH_SYS flavor no real authentication or server-side credential is verified, so an unauthenticated host that can reach TCP/2049 can obtain a delegation and trigger the conflicting-open recall.\nUI:N - The recall, the failed callback queueing and the concurrent nfs4_laundromat scan all happen autonomously in the server; no administrator or user action on the victim is needed.\nS:U - The faulty locking and its consequences are confined to the nfsd/VFS lease code within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:N - The defect is purely a lock-ordering/refcount-release issue; no attacker-readable memory is disclosed and nothing is returned to the client on this path.\nI:N - No memory corruption, out-of-bounds write, or state modification occurs \u2014 the reference count ends at the same value either way, so no integrity primitive is created.\nA:H - Calling nfs4_put_stid() under ctx->flc_lock introduces an flc_lock -> cl_lock ordering (via might_lock() and refcount_dec_and_lock()) that inverts the cl_lock -> flc_lock order taken by nfs4_laundromat()/nfs4_anylock_blockers(), producing a circular-locking-dependency report that taints the kernel, permanently disables lock validation, and aborts the machine on panic_on_warn configurations; should the delegation's lease reference ever not be held, the same path is a hard spinlock ABBA deadlock that hangs the NFS server."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/nfsd/nfs4state.c"], "versions": [{"version": "b874cdef4e67e5150e07eff0eae1cbb21fb92da1", "lessThan": "b9bbe8f9d5663311d06667ce36d6ed255ead1a26", "status": "affected", "versionType": "git"}, {"version": "cdb796137c57e68ca34518d53be53b679351eb86", "lessThan": "a70832d3555987035fc430ccd703acd89393eadb", "status": "affected", "versionType": "git"}, {"version": "d96587cc93ec369031bcd7658c6adc719873c9fd", "lessThan": "ba903539fff745d592d893c71b30e5e268a95413", "status": "affected", "versionType": "git"}, {"version": "9a81cde8c7ce65dd90fb47ceea93a45fc1a2fbd1", "lessThan": "7d192e27a431026c58d60edf66dc6cd98d0c01fc", "status": "affected", "versionType": "git"}, {"version": "cad3479b63661a399c9df1d0b759e1806e2df3c8", "lessThan": "a7fce086f6ca84db409b9d58493ea77c1978897c", "status": "affected", "versionType": "git"}, {"version": "133f5e2a37ce08c82d24e8fba65e0a81deae4609", "lessThan": "14985d66b9b99c12995dd99d1c6c8dec4114c2a5", "status": "affected", "versionType": "git"}, {"version": "230ca758453c63bd38e4d9f4a21db698f7abada8", "lessThan": "a1d14d931bf700c1025db8c46d6731aa5cf440f9", "status": "affected", "versionType": "git"}, {"version": "63b91c8ff4589f5263873b24c052447a28e10ef7", "status": "affected", "versionType": "git"}, {"version": "6.13.11", "lessThan": "6.14", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/nfsd/nfs4state.c"], "versions": [{"version": "5.10.236", "lessThan": "5.10.237", "status": "affected", "versionType": "semver"}, {"version": "5.15.180", "lessThan": "5.15.181", "status": "affected", "versionType": "semver"}, {"version": "6.1.134", "lessThan": "6.1.135", "status": "affected", "versionType": "semver"}, {"version": "6.6.87", "lessThan": "6.6.88", "status": "affected", "versionType": "semver"}, {"version": "6.12.23", "lessThan": "6.12.25", "status": "affected", "versionType": "semver"}, {"version": "6.14.2", "lessThan": "6.14.4", "status": "affected", "versionType": "semver"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.10.236", "versionEndExcluding": "5.10.237"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.180", "versionEndExcluding": "5.15.181"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.134", "versionEndExcluding": "6.1.135"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.87", "versionEndExcluding": "6.6.88"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.23", "versionEndExcluding": "6.12.25"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14.2", "versionEndExcluding": "6.14.4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13.11"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/b9bbe8f9d5663311d06667ce36d6ed255ead1a26"}, {"url": "https://git.kernel.org/stable/c/a70832d3555987035fc430ccd703acd89393eadb"}, {"url": "https://git.kernel.org/stable/c/ba903539fff745d592d893c71b30e5e268a95413"}, {"url": "https://git.kernel.org/stable/c/7d192e27a431026c58d60edf66dc6cd98d0c01fc"}, {"url": "https://git.kernel.org/stable/c/a7fce086f6ca84db409b9d58493ea77c1978897c"}, {"url": "https://git.kernel.org/stable/c/14985d66b9b99c12995dd99d1c6c8dec4114c2a5"}, {"url": "https://git.kernel.org/stable/c/a1d14d931bf700c1025db8c46d6731aa5cf440f9"}], "title": "nfsd: decrease sc_count directly if fail to queue dl_recall", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"title": "CVE Program Container", "references": [{"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"}, {"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T19:56:48.360Z"}}]}}

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"cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*", "matchCriteriaId": "FA6FEEC2-9F11-4643-8827-749718254FED", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: decrease sc_count directly if fail to queue dl_recall\n\nA deadlock warning occurred when invoking nfs4_put_stid following a failed\ndl_recall queue operation:\n T1 T2\n nfs4_laundromat\n nfs4_get_client_reaplist\n nfs4_anylock_blockers\n__break_lease\n spin_lock // ctx->flc_lock\n spin_lock // clp->cl_lock\n nfs4_lockowner_has_blockers\n locks_owner_has_blockers\n spin_lock // flctx->flc_lock\n nfsd_break_deleg_cb\n nfsd_break_one_deleg\n nfs4_put_stid\n refcount_dec_and_lock\n spin_lock // clp->cl_lock\n\nWhen a file is opened, an nfs4_delegation is allocated with sc_count\ninitialized to 1, and the file_lease holds a reference to the delegation.\nThe file_lease is then associated with the file through kernel_setlease.\n\nThe disassociation is performed in nfsd4_delegreturn via the following\ncall chain:\nnfsd4_delegreturn --> destroy_delegation --> destroy_unhashed_deleg -->\nnfs4_unlock_deleg_lease --> kernel_setlease --> generic_delete_lease\nThe corresponding sc_count reference will be released after this\ndisassociation.\n\nSince nfsd_break_one_deleg executes while holding the flc_lock, the\ndisassociation process becomes blocked when attempting to acquire flc_lock\nin generic_delete_lease. This means:\n1) sc_count in nfsd_break_one_deleg will not be decremented to 0;\n2) The nfs4_put_stid called by nfsd_break_one_deleg will not attempt to\nacquire cl_lock;\n3) Consequently, no deadlock condition is created.\n\nGiven that sc_count in nfsd_break_one_deleg remains non-zero, we can\nsafely perform refcount_dec on sc_count directly. This approach\neffectively avoids triggering deadlock warnings."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: nfsd: disminuir sc_count directamente si no se puede poner en cola dl_recall Se produjo una advertencia de bloqueo al invocar nfs4_put_stid despu\u00e9s de una operaci\u00f3n de cola dl_recall fallida: T1 T2 nfs4_laundromat nfs4_get_client_reaplist nfs4_anylock_blockers __break_lease spin_lock // ctx->flc_lock spin_lock // clp->cl_lock nfs4_lockowner_has_blockers locks_owner_has_blockers spin_lock // flctx->flc_lock nfsd_break_deleg_cb nfsd_break_one_deleg nfs4_put_stid refcount_dec_and_lock spin_lock // clp->cl_lock Cuando se abre un archivo, se genera una nfs4_delegation asignado con sc_count inicializado a 1, y el file_lease contiene una referencia a la delegaci\u00f3n. El file_lease se asocia entonces con el archivo a trav\u00e9s de kernel_setlease. La disociaci\u00f3n se realiza en nfsd4_delegreturn mediante la siguiente cadena de llamadas: nfsd4_delegreturn --> destroy_delegation --> destroy_unhashed_deleg --> nfs4_unlock_deleg_lease --> kernel_setlease --> generic_delete_lease La referencia sc_count correspondiente se liberar\u00e1 despu\u00e9s de esta disociaci\u00f3n. Dado que nfsd_break_one_deleg se ejecuta mientras mantiene el flc_lock, el proceso de disociaci\u00f3n se bloquea al intentar adquirir flc_lock en generic_delete_lease. Esto significa: 1) sc_count en nfsd_break_one_deleg no se decrementar\u00e1 a 0; 2) El `nfs4_put_stid` llamado por `nfsd_break_one_deleg` no intentar\u00e1 adquirir `cl_lock`; 3) Por consiguiente, no se crea ninguna condici\u00f3n de interbloqueo. Dado que `sc_count` en `nfsd_break_one_deleg` permanece distinto de cero, podemos ejecutar `refcount_dec` en `sc_count` directamente. Este enfoque evita eficazmente la activaci\u00f3n de advertencias de interbloqueo."}], "id": "CVE-2025-37871", "lastModified": "2026-07-30T06:22:24.690", "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": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2025-05-09T07:16:08.210", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/14985d66b9b99c12995dd99d1c6c8dec4114c2a5"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7d192e27a431026c58d60edf66dc6cd98d0c01fc"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a1d14d931bf700c1025db8c46d6731aa5cf440f9"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a70832d3555987035fc430ccd703acd89393eadb"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a7fce086f6ca84db409b9d58493ea77c1978897c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b9bbe8f9d5663311d06667ce36d6ed255ead1a26"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ba903539fff745d592d893c71b30e5e268a95413"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"], "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"], "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: nfsd: decrease sc_count directly if fail to queue dl_recall", "id": "2365278", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2365278"}, "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": ["In the Linux kernel, the following vulnerability has been resolved:\nnfsd: decrease sc_count directly if fail to queue dl_recall\nA deadlock warning occurred when invoking nfs4_put_stid following a failed\ndl_recall queue operation:\nT1 T2\nnfs4_laundromat\nnfs4_get_client_reaplist\nnfs4_anylock_blockers\n__break_lease\nspin_lock // ctx->flc_lock\nspin_lock // clp->cl_lock\nnfs4_lockowner_has_blockers\nlocks_owner_has_blockers\nspin_lock // flctx->flc_lock\nnfsd_break_deleg_cb\nnfsd_break_one_deleg\nnfs4_put_stid\nrefcount_dec_and_lock\nspin_lock // clp->cl_lock\nWhen a file is opened, an nfs4_delegation is allocated with sc_count\ninitialized to 1, and the file_lease holds a reference to the delegation.\nThe file_lease is then associated with the file through kernel_setlease.\nThe disassociation is performed in nfsd4_delegreturn via the following\ncall chain:\nnfsd4_delegreturn --> destroy_delegation --> destroy_unhashed_deleg -->\nnfs4_unlock_deleg_lease --> kernel_setlease --> generic_delete_lease\nThe corresponding sc_count reference will be released after this\ndisassociation.\nSince nfsd_break_one_deleg executes while holding the flc_lock, the\ndisassociation process becomes blocked when attempting to acquire flc_lock\nin generic_delete_lease. This means:\n1) sc_count in nfsd_break_one_deleg will not be decremented to 0;\n2) The nfs4_put_stid called by nfsd_break_one_deleg will not attempt to\nacquire cl_lock;\n3) Consequently, no deadlock condition is created.\nGiven that sc_count in nfsd_break_one_deleg remains non-zero, we can\nsafely perform refcount_dec on sc_count directly. This approach\neffectively avoids triggering deadlock warnings."], "name": "CVE-2025-37871", "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": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "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": "2025-05-09T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-37871\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-37871\nhttps://lore.kernel.org/linux-cve-announce/2025050959-CVE-2025-37871-937a@gregkh/T"], "threat_severity": "Moderate"}

{}