{"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":"2026-09-14T12:01:59.946Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-14T12:01:59.946Z"},"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-rc1","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-rc1"}]}]}],"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"}}}}