{"id":"CVE-2026-63978","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-63978","generatedAt":"2026-10-28T00:28:31.712Z","title":"In the Linux kernel, the following vulnerability has been resolved: net/handshake: Drain pending requests at net namespace exit The arguments to list_splice_init() in handshake_net_exit() are reversed.","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/handshake: Drain pending requests at net namespace exit\n\nThe arguments to list_splice_init() in handshake_net_exit() are\nreversed. The call moves the local empty \"requests\" list onto\nhn->hn_requests, leaving the local list empty, so the subsequent\ndrain loop runs zero iterations. Pending handshake requests that\nhad not yet been accepted are not torn down when the net namespace\nis destroyed; each one keeps a reference on a socket file and on\nthe handshake_req allocation.\n\nPass the source and destination in the documented order\n(list_splice_init(list, head) moves list onto head) so the pending\nlist is transferred to the local scratch list and drained through\nhandshake_complete().\n\nFixing the splice direction exposes a list-corruption race. After\nthe splice each req->hr_list still has non-empty link pointers,\nthreading the stack-local scratch list rather than hn_requests.\nA concurrent handshake_req_cancel() -- for example, from sunrpc's\nTLS timeout on a kernel socket whose netns reference was not\ntaken -- finds the request through the rhashtable, calls\nremove_pending(), and sees !list_empty(&req->hr_list).\n__remove_pending_locked() then list_del_init()s an entry off the\nscratch list while the drain iterates, corrupting it. The same\ncall arriving after the drain loop has run list_del() on an\nentry hits LIST_POISON instead.\n\nHave remove_pending() check HANDSHAKE_F_NET_DRAINING under\nhn_lock and report not-found when drain is in progress. The\ndrain has already taken ownership; handshake_complete()'s existing\ntest_and_set on HANDSHAKE_F_REQ_COMPLETED still arbitrates\nbetween drain and cancel for who calls the consumer's hp_done. Use\nlist_del_init() rather than list_del() in the drain so req->hr_list\ndoes not carry LIST_POISON after drain releases the entry.\n\nThe DRAINING guard in remove_pending() makes cancel return false,\nbut cancel still falls through to test_and_set_bit on\nHANDSHAKE_F_REQ_COMPLETED and drops the request's hr_file reference.\nWithout another pin, if that is the last reference, sk_destruct frees\nthe request while it is still linked on the drain loop's local list.\nPin each request's hr_file under hn_lock before releasing the list,\nand drop that drain pin after the loop finishes with the request.","published":"2026-07-19T16:17:17.000Z","lastModified":"2026-10-21T13:19:18.000Z","status":"Undergoing Analysis","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-362"],"affected":[],"epss":{"score":0.00518,"percentile":0.4381,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.52%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/2bf24a7e190aae0ea47c78099938ae056c622e44","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8c35539db0ab0bfa1ea44efab00b053261a69469","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ea5fe6a73ca57e5150b8a38b341aef2636eb72f0","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ee4b2ba9d30155f9945811cd3c0c1b06d45787a9","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63978","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}