GHSA-M7R7-C74X-X286
Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-21 15:31In the Linux kernel, the following vulnerability has been resolved:
NFSD: Guard admin state-revocation walks with NFSD_NET_UP
Writing to /proc/fs/nfsd/unlock_filesystem, or sending the NFSD_CMD_UNLOCK_FILESYSTEM or NFSD_CMD_UNLOCK_EXPORT netlink command, walks the NFSv4 client hash tables to revoke open state and cancel async COPY operations. All three handlers gate that walk on nn->nfsd_serv, but a listener added via portlist or netlink listener_set sets nn->nfsd_serv before any nfsd thread starts. nfsd_startup_net() has not yet allocated nn->conf_id_hashtbl, so the walkers dereference a NULL table. A local administrator with CAP_SYS_ADMIN can crash the kernel this way without ever starting the server.
nn->nfsd_serv is set when the service is created, which precedes table allocation. NFSD_NET_UP instead brackets the window where the tables are live: set at the end of nfsd_startup_net() and cleared in nfsd_shutdown_net() after they are freed, both under nfsd_mutex. Gating the three unlock paths on NFSD_NET_UP fixes the startup-time NULL dereference while preserving the earlier post-shutdown use-after-free fix.
{
"affected": [],
"aliases": [
"CVE-2026-90039"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-16T11:17:17Z",
"severity": null
},
"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.",
"id": "GHSA-m7r7-c74x-x286",
"modified": "2026-09-21T15:31:42Z",
"published": "2026-09-16T12:30:46Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90039"
},
{
"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": "WEB",
"url": "https://git.kernel.org/stable/c/73bf459d696ecf207a9037bf9bb70c51a459469e"
}
],
"schema_version": "1.4.0",
"severity": []
}
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