{"cve":"CVE-2025-21806","nvd":{"published":"2025-02-27T20:16:03.220","modified":"2026-10-15T02:17:36.827","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: let net.core.dev_weight always be non-zero\n\nThe following problem was encountered during stability test:\n\n(NULL net_device): NAPI poll function process_backlog+0x0/0x530 \\\n\treturned 1, exceeding its budget of 0.\n------------[ cut here ]------------\nlist_add double add: new=ffff88905f746f48, prev=ffff88905f746f48, \\\n\tnext=ffff88905f746e40.\nWARNING: CPU: 18 PID: 5462 at lib/list_debug.c:35 \\\n\t__list_add_valid_or_report+0xf3/0x130\nCPU: 18 UID: 0 PID: 5462 Comm: ping Kdump: loaded Not tainted 6.13.0-rc7+\nRIP: 0010:__list_add_valid_or_report+0xf3/0x130\nCall Trace:\n? __warn+0xcd/0x250\n? __list_add_valid_or_report+0xf3/0x130\nenqueue_to_backlog+0x923/0x1070\nnetif_rx_internal+0x92/0x2b0\n__netif_rx+0x15/0x170\nloopback_xmit+0x2ef/0x450\ndev_hard_start_xmit+0x103/0x490\n__dev_queue_xmit+0xeac/0x1950\nip_finish_output2+0x6cc/0x1620\nip_output+0x161/0x270\nip_push_pending_frames+0x155/0x1a0\nraw_sendmsg+0xe13/0x1550\n__sys_sendto+0x3bf/0x4e0\n__x64_sys_sendto+0xdc/0x1b0\ndo_syscall_64+0x5b/0x170\nentry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nThe reproduction command is as follows:\n  sysctl -w net.core.dev_weight=0\n  ping 127.0.0.1\n\nThis is because when the napi's weight is set to 0, process_backlog() may\nreturn 0 and clear the NAPI_STATE_SCHED bit of napi->state, causing this\nnapi to be re-polled in net_rx_action() until __do_softirq() times out.\nSince the NAPI_STATE_SCHED bit has been cleared, napi_schedule_rps() can\nbe retriggered in enqueue_to_backlog(), causing this issue.\n\nMaking the napi's weight always non-zero solves this problem.\n\nTriggering this issue requires system-wide admin (setting is\nnot namespaced).","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/0e2f1d93d287d544d26f8ff293ea820a8079b9f8","https://git.kernel.org/stable/c/1489824e5226a26841c70639ebd2d1aed390764b","https://git.kernel.org/stable/c/33e2168788f8fb5cb8bd4f36cb1ef37d1d34dada","https://git.kernel.org/stable/c/5860abbf15eeb61838b5e32e721ba67b0aa84450","https://git.kernel.org/stable/c/6ce38b5a6a49e65bad163162a54cb3f104c40b48"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:59:48.811064707+00:00"},"epss":{"cve":"CVE-2025-21806","score":0.00227,"percentile":0.1335,"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."]}