{"id":"CVE-2026-89702","state":"PUBLISHED","title":"nfsd: size fh_verify server sockaddr slot by xpt_locallen","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: size fh_verify server sockaddr slot by xpt_locallen\n\nThe nfsd_fh_verify and nfsd_fh_verify_err tracepoints declare the\nserver sockaddr slot sized by xpt_remotelen but fill it from\nxpt_local using xpt_locallen:\n\n    TP_STRUCT__entry(\n            ...\n            __sockaddr(server, rqstp->rq_xprt->xpt_remotelen)\n            ...\n    )\n    TP_fast_assign(\n            ...\n            __assign_sockaddr(server, &rqstp->rq_xprt->xpt_local,\n                              rqstp->rq_xprt->xpt_locallen);\n            ...\n    )\n\nWhen xpt_locallen exceeds xpt_remotelen, __assign_sockaddr's memcpy\nwrites past the reserved ring-buffer slot. In the reverse direction\n(xpt_locallen < xpt_remotelen) the slot is oversized and the\nunwritten tail leaks prior ring-buffer contents to trace consumers.\n\nThe write-past-end case is reachable on NFS/UDP. svc_xprt_set_remote()\nis only called from svc_tcp_accept() (net/sunrpc/svcsock.c) and from\nthe RDMA connect path; svc_create_socket() for UDP calls only\nsvc_xprt_set_local(), so xpt_remotelen stays 0 for the xprt's\nlifetime. Every fh_verify trace for an NFSv2/v3-over-UDP request\nthen copies 16 or 28 bytes from xpt_local into a zero-byte slot.\n\nThe other NFSD tracepoints that record the server address\n(NFSD_TRACE_PROC_CALL_FIELDS, NFSD_TRACE_PROC_RES_FIELDS,\nSVC_RQST_ENDPOINT_FIELDS) already size the server slot by\nxpt_locallen; nfsd_fh_verify and nfsd_fh_verify_err were the only\nexceptions.\n\nFix by sizing the server slot with xpt_locallen so the declared slot\nmatches the copy length. The client slot and its assignment already\nagree on xpt_remotelen and are left untouched.","publishedAt":"2026-09-11T19:46:19.537Z","updatedAt":"2026-10-30T12:32:45.423Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"dcbebc86850324fbe0a993ce352f0539cd98038a","status":"affected","lessThan":"4c7569ad68fc8b86ca40c7e56ef21460c0344955","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"50d9d581d2af80799125ee62617d37e9b6b476a7","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"1c6a4d6c20fd42552ffc2c3dfaed2139c9477ee5","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"95d064f9828a20ccca5ae90a17be3e2076f25272","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"7ff8d6363cffff45654ea85e319f7c0c54226012","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"719a10e3f5f868c3c4ac3cf3648c5775d12034bd","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"71d068490098b1d23c63b2345e40675d3a1ca763","versionType":"git"},{"version":"62980365d6e894234b29f44fb2bfad4f7f8bb824","status":"affected","versionType":"git"},{"version":"5.15.154","status":"affected","lessThan":"5.15.224","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/trace.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.0","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/trace.h"]}],"references":["https://git.kernel.org/stable/c/4c7569ad68fc8b86ca40c7e56ef21460c0344955","https://git.kernel.org/stable/c/50d9d581d2af80799125ee62617d37e9b6b476a7","https://git.kernel.org/stable/c/1c6a4d6c20fd42552ffc2c3dfaed2139c9477ee5","https://git.kernel.org/stable/c/95d064f9828a20ccca5ae90a17be3e2076f25272","https://git.kernel.org/stable/c/7ff8d6363cffff45654ea85e319f7c0c54226012","https://git.kernel.org/stable/c/719a10e3f5f868c3c4ac3cf3648c5775d12034bd","https://git.kernel.org/stable/c/71d068490098b1d23c63b2345e40675d3a1ca763"],"weaknesses":[],"ingestedAt":"2026-10-30T12:52:04.348Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89702.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89702","state":"PUBLISHED","datePublished":"2026-09-11T19:46:19.537Z","dateUpdated":"2026-10-30T12:32:45.423Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.750Z"},"containers":{"cna":{"title":"nfsd: size fh_verify server sockaddr slot by xpt_locallen","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: size fh_verify server sockaddr slot by xpt_locallen\n\nThe nfsd_fh_verify and nfsd_fh_verify_err tracepoints declare the\nserver sockaddr slot sized by xpt_remotelen but fill it from\nxpt_local using xpt_locallen:\n\n    TP_STRUCT__entry(\n            ...\n            __sockaddr(server, rqstp->rq_xprt->xpt_remotelen)\n            ...\n    )\n    TP_fast_assign(\n            ...\n            __assign_sockaddr(server, &rqstp->rq_xprt->xpt_local,\n                              rqstp->rq_xprt->xpt_locallen);\n            ...\n    )\n\nWhen xpt_locallen exceeds xpt_remotelen, __assign_sockaddr's memcpy\nwrites past the reserved ring-buffer slot. In the reverse direction\n(xpt_locallen < xpt_remotelen) the slot is oversized and the\nunwritten tail leaks prior ring-buffer contents to trace consumers.\n\nThe write-past-end case is reachable on NFS/UDP. svc_xprt_set_remote()\nis only called from svc_tcp_accept() (net/sunrpc/svcsock.c) and from\nthe RDMA connect path; svc_create_socket() for UDP calls only\nsvc_xprt_set_local(), so xpt_remotelen stays 0 for the xprt's\nlifetime. Every fh_verify trace for an NFSv2/v3-over-UDP request\nthen copies 16 or 28 bytes from xpt_local into a zero-byte slot.\n\nThe other NFSD tracepoints that record the server address\n(NFSD_TRACE_PROC_CALL_FIELDS, NFSD_TRACE_PROC_RES_FIELDS,\nSVC_RQST_ENDPOINT_FIELDS) already size the server slot by\nxpt_locallen; nfsd_fh_verify and nfsd_fh_verify_err were the only\nexceptions.\n\nFix by sizing the server slot with xpt_locallen so the declared slot\nmatches the copy length. The client slot and its assignment already\nagree on xpt_remotelen and are left untouched."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"dcbebc86850324fbe0a993ce352f0539cd98038a","status":"affected","lessThan":"4c7569ad68fc8b86ca40c7e56ef21460c0344955","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"50d9d581d2af80799125ee62617d37e9b6b476a7","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"1c6a4d6c20fd42552ffc2c3dfaed2139c9477ee5","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"95d064f9828a20ccca5ae90a17be3e2076f25272","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"7ff8d6363cffff45654ea85e319f7c0c54226012","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"719a10e3f5f868c3c4ac3cf3648c5775d12034bd","versionType":"git"},{"version":"051382885552e12541cc0ebf82092be374a9ed2a","status":"affected","lessThan":"71d068490098b1d23c63b2345e40675d3a1ca763","versionType":"git"},{"version":"62980365d6e894234b29f44fb2bfad4f7f8bb824","status":"affected","versionType":"git"},{"version":"5.15.154","status":"affected","lessThan":"5.15.224","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/trace.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.0","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/trace.h"]}],"references":[{"url":"https://git.kernel.org/stable/c/4c7569ad68fc8b86ca40c7e56ef21460c0344955"},{"url":"https://git.kernel.org/stable/c/50d9d581d2af80799125ee62617d37e9b6b476a7"},{"url":"https://git.kernel.org/stable/c/1c6a4d6c20fd42552ffc2c3dfaed2139c9477ee5"},{"url":"https://git.kernel.org/stable/c/95d064f9828a20ccca5ae90a17be3e2076f25272"},{"url":"https://git.kernel.org/stable/c/7ff8d6363cffff45654ea85e319f7c0c54226012"},{"url":"https://git.kernel.org/stable/c/719a10e3f5f868c3c4ac3cf3648c5775d12034bd"},{"url":"https://git.kernel.org/stable/c/71d068490098b1d23c63b2345e40675d3a1ca763"}],"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 nfsd_fh_verify and nfsd_fh_verify_err tracepoints run in the in-kernel NFS server while handling NFSv2/v3 RPCs on UDP/2049; a remote packet reaches svc_udp_recvfrom, svc_process, nfsd_proc_getattr/nfsd3_proc_getattr, then fh_verify.\nAC:L - With the nfsd_fh_verify events enabled (a realistic nfsd tracing/perf deployment), every UDP fh_verify deterministically memcpy's 16 or 28 bytes of xpt_local into a 0-byte slot; no race, layout guess, or attacker-uncontrollable condition is required.\nPR:N - AUTH_NULL and AUTH_SYS verify no credentials, and GETATTR uses NFSD_MAY_NOP so a dummy filehandle still hits fh_verify (and nfsd_fh_verify_err on lookup failure); a UDP source-IP spoof or wildcard export satisfies the IP map without an authenticated principal.\nUI:N - The attacker sends crafted NFS/UDP RPCs unilaterally; no administrator or victim-client action is required at exploitation time, and tracing already being enabled is the scored configuration rather than user interaction.\nS:U - The overflow corrupts the host kernel's ftrace/perf ring buffer inside the NFS server's own kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - When the reserved sockaddr slot is larger than xpt_locallen, leftover prior ring-buffer contents including kernel pointers from other events leak to trace consumers; the UDP out-of-bounds write can also corrupt adjacent event headers so later parses treat neighbouring kernel memory as payload.\nI:H - On NFS/UDP, xpt_remotelen stays 0 so __assign_sockaddr copies 16 or 28 bytes of xpt_local past the reserved dynamic array into subsequent ring-buffer bytes and potentially the next sub-buffer page header, which is an out-of-bounds kernel write.\nA:H - Corrupting ring-buffer event headers or the next sub-buffer page metadata can oops or panic the tracer or hang consumers, and a remote peer can repeat the UDP request to force the overflow until the kernel faults."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:32:45.423Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.154","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.12.109"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}