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vuln-cve/data/2025/37xxx/CVE-2025-37871.json
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{
"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 — 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 — 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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