{"cve":"CVE-2025-68372","nvd":{"published":"2025-12-24T11:16:00.777","modified":"2026-10-13T11:10:00.203","status":"Deferred","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnbd: defer config put in recv_work\n\nThere is one uaf issue in recv_work when running NBD_CLEAR_SOCK and\nNBD_CMD_RECONFIGURE:\n  nbd_genl_connect     // conf_ref=2 (connect and recv_work A)\n  nbd_open\t       // conf_ref=3\n  recv_work A done     // conf_ref=2\n  NBD_CLEAR_SOCK       // conf_ref=1\n  nbd_genl_reconfigure // conf_ref=2 (trigger recv_work B)\n  close nbd\t       // conf_ref=1\n  recv_work B\n    config_put         // conf_ref=0\n    atomic_dec(&config->recv_threads); -> UAF\n\nOr only running NBD_CLEAR_SOCK:\n  nbd_genl_connect   // conf_ref=2\n  nbd_open \t     // conf_ref=3\n  NBD_CLEAR_SOCK     // conf_ref=2\n  close nbd\n    nbd_release\n      config_put     // conf_ref=1\n  recv_work\n    config_put \t     // conf_ref=0\n    atomic_dec(&config->recv_threads); -> UAF\n\nCommit 87aac3a80af5 (\"nbd: call nbd_config_put() before notifying the\nwaiter\") moved nbd_config_put() to run before waking up the waiter in\nrecv_work, in order to ensure that nbd_start_device_ioctl() would not\nbe woken up while nbd->task_recv was still uncleared.\n\nHowever, in nbd_start_device_ioctl(), after being woken up it explicitly\ncalls flush_workqueue() to make sure all current works are finished.\nTherefore, there is no need to move the config put ahead of the wakeup.\n\nMove nbd_config_put() to the end of recv_work, so that the reference is\nheld for the whole lifetime of the worker thread. This makes sure the\nconfig cannot be freed while recv_work is still running, even if clear\n+ reconfigure interleave.\n\nIn addition, we don't need to worry about recv_work dropping the last\nnbd_put (which causes deadlock):\n\npath A (netlink with NBD_CFLAG_DESTROY_ON_DISCONNECT):\n  connect  // nbd_refs=1 (trigger recv_work)\n  open nbd // nbd_refs=2\n  NBD_CLEAR_SOCK\n  close nbd\n    nbd_release\n      nbd_disconnect_and_put\n        flush_workqueue // recv_work done\n      nbd_config_put\n        nbd_put // nbd_refs=1\n      nbd_put // nbd_refs=0\n        queue_work\n\npath B (netlink without NBD_CFLAG_DESTROY_ON_DISCONNECT):\n  connect  // nbd_refs=2 (trigger recv_work)\n  open nbd // nbd_refs=3\n  NBD_CLEAR_SOCK // conf_refs=2\n  close nbd\n    nbd_release\n      nbd_config_put // conf_refs=1\n      nbd_put // nbd_refs=2\n  recv_work done // conf_refs=0, nbd_refs=1\n  rmmod // nbd_refs=0\n\nDepends-on: e2daec488c57 (\"nbd: Fix hungtask when nbd_config_put\")","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/198aa230a6f8c1f6af7ed26b29180749c3e79e4d","https://git.kernel.org/stable/c/1ba2ced2bbdf7e64a30c3e88c70ea8bc208d1509","https://git.kernel.org/stable/c/3692884bd6187d89d41eef81e5a9724519fd01c1","https://git.kernel.org/stable/c/443a1721806b6ff6303b5229e9811d68172d622f","https://git.kernel.org/stable/c/6b69593f72e1bfba6ca47ca8d9b619341fded7d6"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:17:07.138532058+00:00"},"epss":{"cve":"CVE-2025-68372","score":0.00198,"percentile":0.09463,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}