{"cve":"CVE-2026-43385","nvd":{"published":"2026-05-08T15:16:49.830","modified":"2026-06-17T10:49:29.980","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: Fix rcu_tasks stall in threaded busypoll\n\nI was debugging a NIC driver when I noticed that when I enable\nthreaded busypoll, bpftrace hangs when starting up. dmesg showed:\n\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 10658 jiffies old.\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 40793 jiffies old.\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 131273 jiffies old.\n  rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 402058 jiffies old.\n  INFO: rcu_tasks detected stalls on tasks:\n  00000000769f52cd: .N nvcsw: 2/2 holdout: 1 idle_cpu: -1/64\n  task:napi/eth2-8265  state:R  running task     stack:0     pid:48300 tgid:48300 ppid:2      task_flags:0x208040 flags:0x00004000\n  Call Trace:\n   <TASK>\n   ? napi_threaded_poll_loop+0x27c/0x2c0\n   ? __pfx_napi_threaded_poll+0x10/0x10\n   ? napi_threaded_poll+0x26/0x80\n   ? kthread+0xfa/0x240\n   ? __pfx_kthread+0x10/0x10\n   ? ret_from_fork+0x31/0x50\n   ? __pfx_kthread+0x10/0x10\n   ? ret_from_fork_asm+0x1a/0x30\n   </TASK>\n\nThe cause is that in threaded busypoll, the main loop is in\nnapi_threaded_poll rather than napi_threaded_poll_loop, where the\nlatter rarely iterates more than once within its loop. For\nrcu_softirq_qs_periodic inside napi_threaded_poll_loop to report its\nqs state, the last_qs must be 100ms behind, and this can't happen\nbecause napi_threaded_poll_loop rarely iterates in threaded busypoll,\nand each time napi_threaded_poll_loop is called last_qs is reset to\nlatest jiffies.\n\nThis patch changes so that in threaded busypoll, last_qs is saved\nin the outer napi_threaded_poll, and whether busy_poll_last_qs\nis NULL indicates whether napi_threaded_poll_loop is called for\nbusypoll. This way last_qs would not reset to latest jiffies on\neach invocation of napi_threaded_poll_loop.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":[],"references":["https://git.kernel.org/stable/c/1a86a1f7d88996085934139fa4c063b6299a2dd3","https://git.kernel.org/stable/c/52459201d0df3fdbb1d281738b7b772e2cacb49c"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:33:55.586217763+00:00"},"epss":{"cve":"CVE-2026-43385","score":0.00344,"percentile":0.27942,"date":"2026-10-31"},"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."]}