{"id":"CVE-2026-90039","summary":"NFSD: Guard admin state-revocation walks with NFSD_NET_UP","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Guard admin state-revocation walks with NFSD_NET_UP\n\nWriting to /proc/fs/nfsd/unlock_filesystem, or sending the\nNFSD_CMD_UNLOCK_FILESYSTEM or NFSD_CMD_UNLOCK_EXPORT netlink command,\nwalks the NFSv4 client hash tables to revoke open state and cancel\nasync COPY operations.  All three handlers gate that walk on\nnn-\u003enfsd_serv, but a listener added via portlist or netlink\nlistener_set sets nn-\u003enfsd_serv before any nfsd thread starts.\nnfsd_startup_net() has not yet allocated nn-\u003econf_id_hashtbl, so the\nwalkers dereference a NULL table.  A local administrator with\nCAP_SYS_ADMIN can crash the kernel this way without ever starting the\nserver.\n\nnn-\u003enfsd_serv is set when the service is created, which precedes\ntable allocation.  NFSD_NET_UP instead brackets the window where the\ntables are live: set at the end of nfsd_startup_net() and cleared in\nnfsd_shutdown_net() after they are freed, both under nfsd_mutex.\nGating the three unlock paths on NFSD_NET_UP fixes the startup-time\nNULL dereference while preserving the earlier post-shutdown\nuse-after-free fix.","modified":"2026-09-18T03:48:34.966504289Z","published":"2026-09-16T10:33:38.091Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90039.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0146467a2fce845cb6629979c3e9c58dd3d3a6a3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/104a51265042b4424085741c963cb858ac29ec0b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2f3e6638aebc0ab8afb8b4e9816ea9a1cad85378"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90039.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90039"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"1ac3629bf012592cb0320e52a1cceb319a05ad17"},{"fixed":"104a51265042b4424085741c963cb858ac29ec0b"},{"fixed":"0146467a2fce845cb6629979c3e9c58dd3d3a6a3"},{"fixed":"2f3e6638aebc0ab8afb8b4e9816ea9a1cad85378"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90039.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.9.0"},{"fixed":"6.18.51"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90039.json"}}],"schema_version":"1.9.0"}