{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2021-47506", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-05-22T06:20:56.205Z", "datePublished": "2024-05-24T15:01:52.746Z", "dateUpdated": "2026-08-05T08:48:10.240Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:48:10.240Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix use-after-free due to delegation race\n\nA delegation break could arrive as soon as we've called vfs_setlease. A\ndelegation break runs a callback which immediately (in\nnfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we\nthen exit nfs4_set_delegation without hashing the delegation, it will be\nfreed as soon as the callback is done with it, without ever being\nremoved from del_recall_lru.\n\nSymptoms show up later as use-after-free or list corruption warnings,\nusually in the laundromat thread.\n\nI suspect aba2072f4523 \"nfsd: grant read delegations to clients holding\nwrites\" made this bug easier to hit, but I looked as far back as v3.0\nand it looks to me it already had the same problem. So I'm not sure\nwhere the bug was introduced; it may have been there from the beginning." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - The vulnerable path is in the in-kernel NFS server (nfs4_set_delegation / nfsd4_cb_recall_prepare in fs/nfsd/nfs4state.c), reached when a remote NFSv4 client issues OPEN compounds over TCP/UDP 2049 that attempt to grant a read delegation.\nAC:L - A remote attacker controls both sides of the race by opening/requesting a delegation on one NFS client/session while concurrently issuing a conflicting open (e.g. write) from another client or session slot on separate nfsd threads, so success does not depend on conditions outside attacker influence.\nPR:N - Typical nfsd deployments use AUTH_SYS/AUTH_NULL with IP-based exports and no cryptographic authentication, so any host allowed by the export can EXCHANGE_ID/CREATE_SESSION/OPEN and exercise the delegation-grant path by self-asserting credentials.\nUI:N - The attacker alone drives the OPEN/delegation grant and the conflicting open that breaks the lease; no victim user or administrator action on the server is required.\nS:U - The use-after-free corrupts kernel slab memory (nfs4_delegation on del_recall_lru) within the host nfsd security authority and does not cross a VM, IOMMU, or other separate boundary.\nC:H - The unhashed delegation is freed while still linked on del_recall_lru; later laundromat traversal is a classic slab UAF that can be groomed/reallocated to disclose arbitrary kernel memory.\nI:H - The same freed nfs4_delegation object remains on del_recall_lru so laundromat list operations write into attacker-reclaimable heap, yielding an arbitrary-write / control-flow hijack primitive.\nA:H - Use-after-free and list corruption of del_recall_lru reliably cause kernel oops/panic in the laundromat thread, fully disrupting availability of the NFS server host." } ] } ], "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": "dff1399f8addf7129c49bb2227469da79cc30b47", "lessThan": "04a8d07f3d58308b92630045560799a3faa3ebce", "status": "affected", "versionType": "git" }, { "version": "dff1399f8addf7129c49bb2227469da79cc30b47", "lessThan": "348714018139c39533c55661a0c7c990671396b4", "status": "affected", "versionType": "git" }, { "version": "dff1399f8addf7129c49bb2227469da79cc30b47", "lessThan": "33645d3e22720cac1e4548f8fef57bf0649536ee", "status": "affected", "versionType": "git" }, { "version": "dff1399f8addf7129c49bb2227469da79cc30b47", "lessThan": "2becaa990b93cbd2928292c0b669d3abb6cf06d4", "status": "affected", "versionType": "git" }, { "version": "dff1399f8addf7129c49bb2227469da79cc30b47", "lessThan": "e0759696de6851d7536efddfdd2dfed4c4df1f09", "status": "affected", "versionType": "git" }, { "version": "dff1399f8addf7129c49bb2227469da79cc30b47", "lessThan": "eeb0711801f5e19ef654371b627682aed3b11373", "status": "affected", "versionType": "git" }, { "version": "dff1399f8addf7129c49bb2227469da79cc30b47", "lessThan": "148c816f10fd11df27ca6a9b3238cdd42fa72cd3", "status": "affected", "versionType": "git" }, { "version": "dff1399f8addf7129c49bb2227469da79cc30b47", "lessThan": "548ec0805c399c65ed66c6641be467f717833ab5", "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/nfsd/nfs4state.c" ], "versions": [ { "version": "3.17", "status": "affected" }, { "version": "0", "lessThan": "3.17", "status": "unaffected", "versionType": "semver" }, { "version": "4.4.296", "lessThanOrEqual": "4.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.9.294", "lessThanOrEqual": "4.9.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.14.259", "lessThanOrEqual": "4.14.*", "status": "unaffected", "versionType": "semver" }, { "version": "4.19.222", "lessThanOrEqual": "4.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.168", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.85", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.8", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.16", "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": "3.17", "versionEndExcluding": "4.4.296" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.17", "versionEndExcluding": "4.9.294" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.17", "versionEndExcluding": "4.14.259" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.17", "versionEndExcluding": "4.19.222" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.17", "versionEndExcluding": "5.4.168" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.17", "versionEndExcluding": "5.10.85" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.17", "versionEndExcluding": "5.15.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.17", "versionEndExcluding": "5.16" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/04a8d07f3d58308b92630045560799a3faa3ebce" }, { "url": "https://git.kernel.org/stable/c/348714018139c39533c55661a0c7c990671396b4" }, { "url": "https://git.kernel.org/stable/c/33645d3e22720cac1e4548f8fef57bf0649536ee" }, { "url": "https://git.kernel.org/stable/c/2becaa990b93cbd2928292c0b669d3abb6cf06d4" }, { "url": "https://git.kernel.org/stable/c/e0759696de6851d7536efddfdd2dfed4c4df1f09" }, { "url": "https://git.kernel.org/stable/c/eeb0711801f5e19ef654371b627682aed3b11373" }, { "url": "https://git.kernel.org/stable/c/148c816f10fd11df27ca6a9b3238cdd42fa72cd3" }, { "url": "https://git.kernel.org/stable/c/548ec0805c399c65ed66c6641be467f717833ab5" } ], "title": "nfsd: fix use-after-free due to delegation race", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "title": "CISA ADP Vulnrichment", "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2021-47506", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2024-05-29T17:04:47.932390Z" } } } ], "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-06-04T17:13:44.394Z" } }, { "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:39:59.751Z" }, "title": "CVE Program Container", "references": [ { "url": "https://git.kernel.org/stable/c/04a8d07f3d58308b92630045560799a3faa3ebce", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/348714018139c39533c55661a0c7c990671396b4", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/33645d3e22720cac1e4548f8fef57bf0649536ee", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/2becaa990b93cbd2928292c0b669d3abb6cf06d4", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/e0759696de6851d7536efddfdd2dfed4c4df1f09", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/eeb0711801f5e19ef654371b627682aed3b11373", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/148c816f10fd11df27ca6a9b3238cdd42fa72cd3", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/548ec0805c399c65ed66c6641be467f717833ab5", "tags": [ "x_transferred" ] } ] } ] } }