{"cve":"CVE-2026-74284","nvd":{"published":"2026-08-15T06:22:27.903","modified":"2026-08-17T06:19:22.257","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_hfsc: Don't make class passive twice\n\nupdate_vf() is called from two places for the same class during a single\ndequeue when the class's child qdisc (e.g. codel/fq_codel) drops its last\npackets while dequeuing:\n\n1. The child calls qdisc_tree_reduce_backlog(), which, now that the child\n   is empty, invokes hfsc_qlen_notify() -> update_vf(cl, 0, 0) and turns\n   the class passive (cl_nactive is decremented up the hierarchy).\n\n2. hfsc_dequeue() then calls update_vf(cl, qdisc_pkt_len(skb), cur_time)\n   to charge the dequeued bytes.\n\nOn the second call the class is already passive, but its child qdisc is\nstill empty, so update_vf() arms go_passive again:\n\n      if (cl->qdisc->q.qlen == 0 && cl->cl_flags & HFSC_FSC)\n              go_passive = 1;\n\nThe leaf is then skipped by the cl_nactive == 0 check inside the loop,\nwhich does not clear go_passive, so the stale go_passive propagates to the\nparent and decrements its cl_nactive a second time. A parent that still\nhas other active children is driven to cl_nactive == 0 and removed from\nthe vttree, even though those siblings are still backlogged. They are\nnever dequeued again and the qdisc stalls.\n\nFix this by only arming go_passive when the class is actually active, so an\nalready-passive class no longer triggers a second passive transition. The\nbyte accounting (cl->cl_total += len) still runs for every ancestor, so\ndequeued bytes continue to be counted exactly once.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/15720cd8fa3fc625146128f89a8e11b0449a20a7","https://git.kernel.org/stable/c/3a49bbae676fef1ffe548971e6229ae2adeb9d10","https://git.kernel.org/stable/c/66dbb13eeb2fc339f8f548a9076be4c1a94857b0","https://git.kernel.org/stable/c/90b662ea25f5e83bb3b8ccec5b93ced810b92fb8","https://git.kernel.org/stable/c/9221a594c72a1446137926d4c2aa04e345f798dc"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:48:17.459049833+00:00"},"epss":{"cve":"CVE-2026-74284","score":0.00216,"percentile":0.12106,"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."]}