{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89674", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.746Z", "datePublished": "2026-09-11T19:45:58.883Z", "dateUpdated": "2026-10-19T08:50:47.609Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:50:47.609Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget\n\nThe XDR buffer size calculation in nfsd4_ff_encode_layoutget() has\nmultiple errors that can result in either an out-of-bounds write or\nleaking uninitialized kernel memory to the client:\n\n - fh_len doesn't account for XDR padding on the file handle data\n - uid and gid lengths use \"8 + len\" but xdr_encode_opaque() actually\n writes \"4 + xdr_align_size(len)\" bytes\n - ds_len omits the flags and stats_collect_hint fields (8 bytes),\n while len's header constant overestimates by 8 bytes -- these\n partially cancel but leave a net mismatch\n\nThe worst case occurs with short strings (e.g. uid=0, gid=0 with an\nodd-sized file handle), where the function writes up to 5 bytes past\nthe reserved XDR buffer. Conversely, when string lengths happen to be\n4-byte aligned, the reservation is too large and stale buffer content\nis sent to the client.\n\nFix this by breaking out every encoded field explicitly in the ds_len\ncalculation, using xdr_align_size() for all variable-length opaque\nfields, and correcting the header constants." } ], "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 bug is in nfsd's pNFS flexfile LAYOUTGET encoder (nfsd4_ff_encode_layoutget). A remote NFSv4.1 client reaches it over TCP/2049 via COMPOUND SEQUENCE, PUTFH, OPEN, and LAYOUTGET on the in-kernel NFS server.\nAC:L - A client that can OPEN a file on a flexfile pNFS export issues LAYOUTGET and hits the miscalculated xdr_reserve_space length. Root-owned files yield uid/gid \"0\", and PUTFH may append 1-3 bytes ignored by fh_verify so fh.size is odd; no race is required.\nPR:N - Typical nfsd deployments accept AUTH_SYS/AUTH_NULL without cryptographic authentication. Any host allowed by the export ACL can EXCHANGE_ID/CREATE_SESSION, PUTFH/OPEN, and LAYOUTGET; no local account on the NFS server is required.\nUI:N - The attacking NFS client drives the compounds that open a file and request a flexfile layout. No victim user action such as mounting a filesystem or opening a file on the server is required.\nS:U - The out-of-bounds write and kernel-memory leak occur in the NFS server host's XDR reply buffer. Impact stays in that kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - When the reservation is too large, stale uninitialized kernel bytes in the RPC reply are sent to the client. The matching out-of-bounds write is kernel memory corruption that can be leveraged for information disclosure per CVSS kernel guidance.\nI:H - Worst case the encoder writes up to 5 bytes past the xdr_reserve_space region, including across a reply-page boundary into adjacent kernel memory. Kernel CNA guidance scores out-of-bounds writes as High integrity impact.\nA:H - A write past the current XDR page (xdr->end) into an unmapped or unrelated page oopses or panics nfsd. The attacker can pad prior COMPOUND ops to place the LAYOUTGET encode at a page boundary and repeat the request to deny service." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/flexfilelayoutxdr.c" ], "versions": [ { "version": "9b9960a0ca4773e21c4b153ed355583946346b25", "lessThan": "3a7fd224df0fbb42167eb1b77be45d72fe0b1098", "status": "affected", "versionType": "git" }, { "version": "9b9960a0ca4773e21c4b153ed355583946346b25", "lessThan": "29e4478e2ed5a227e8f0c33cacb91bf227cedd47", "status": "affected", "versionType": "git" }, { "version": "9b9960a0ca4773e21c4b153ed355583946346b25", "lessThan": "65a72b721943618eeb3a41c8b36e915591f3f83f", "status": "affected", "versionType": "git" }, { "version": "9b9960a0ca4773e21c4b153ed355583946346b25", "lessThan": "bee826c00ac900473f91306f1f3e5a5a81fd4a74", "status": "affected", "versionType": "git" }, { "version": "9b9960a0ca4773e21c4b153ed355583946346b25", "lessThan": "e7d9d23ecd9172f05b09bb678ff22db8e361c428", "status": "affected", "versionType": "git" }, { "version": "9b9960a0ca4773e21c4b153ed355583946346b25", "lessThan": "0380129b1373c437eb35401a174671c8888f4b80", "status": "affected", "versionType": "git" }, { "version": "9b9960a0ca4773e21c4b153ed355583946346b25", "lessThan": "c81cef6a805dec266c10fc4f83c93d6fcf1a2b43", "status": "affected", "versionType": "git" }, { "version": "9b9960a0ca4773e21c4b153ed355583946346b25", "lessThan": "f9868174af49d207fbaf0c5e055d088a983684af", "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/flexfilelayoutxdr.c" ], "versions": [ { "version": "4.8", "status": "affected" }, { "version": "0", "lessThan": "4.8", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "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": "4.8", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/3a7fd224df0fbb42167eb1b77be45d72fe0b1098" }, { "url": "https://git.kernel.org/stable/c/29e4478e2ed5a227e8f0c33cacb91bf227cedd47" }, { "url": "https://git.kernel.org/stable/c/65a72b721943618eeb3a41c8b36e915591f3f83f" }, { "url": "https://git.kernel.org/stable/c/bee826c00ac900473f91306f1f3e5a5a81fd4a74" }, { "url": "https://git.kernel.org/stable/c/e7d9d23ecd9172f05b09bb678ff22db8e361c428" }, { "url": "https://git.kernel.org/stable/c/0380129b1373c437eb35401a174671c8888f4b80" }, { "url": "https://git.kernel.org/stable/c/c81cef6a805dec266c10fc4f83c93d6fcf1a2b43" }, { "url": "https://git.kernel.org/stable/c/f9868174af49d207fbaf0c5e055d088a983684af" } ], "title": "nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget", "x_generator": { "engine": "bippy-1.2.0" } } } }