{"id":"CVE-2026-74284","title":"net/sched: sch_hfsc: Don't make class passive twice","summary":"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.…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7 < a425c82ff06cda5165e0de3de8c2a445ec1f863e","Linux >= a5efc95a33bd4fcb879250852828cc58c7862970 < fc973ecd1a079b9a87c360478542f3a56dea085b","Linux >= 0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87 < 15720cd8fa3fc625146128f89a8e11b0449a20a7","Linux >= 9030a91235ae4845ec71902c3e0cecfc9ed1f2df < b2a017bfcf565721918ec7355a373911d2f2a227","Linux >= d06476714d2819b550e0cc39222347e2c8941c9d < 9221a594c72a1446137926d4c2aa04e345f798dc","Linux >= 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb < 66dbb13eeb2fc339f8f548a9076be4c1a94857b0","Linux >= 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb < 3a49bbae676fef1ffe548971e6229ae2adeb9d10","Linux >= 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb < 90b662ea25f5e83bb3b8ccec5b93ced810b92fb8","Linux 9a5fd5c2f4d4afdd5e405083ee53e0789ce76956","Linux c1175c4ad01dbc9c979d099861fa90a754f72059","Linux >= 5.10.241 < 5.10.261","Linux >= 5.15.190 < 5.15.212","Linux >= 6.1.138 < 6.1.178","Linux >= 6.6.90 < 6.6.145","Linux >= 6.12.28 < 6.12.97","Linux >= 5.4.297 < 5.5","Linux >= 6.14.6 < 6.15","Linux 6.15"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-06T16:55:52.211339Z"},"published":"2026-08-15","updated":"2026-11-06","sourceUpdated":"2026-11-06T17:05:43.463Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-74284","references":[{"url":"https://git.kernel.org/stable/c/a425c82ff06cda5165e0de3de8c2a445ec1f863e"},{"url":"https://git.kernel.org/stable/c/fc973ecd1a079b9a87c360478542f3a56dea085b"},{"url":"https://git.kernel.org/stable/c/15720cd8fa3fc625146128f89a8e11b0449a20a7"},{"url":"https://git.kernel.org/stable/c/b2a017bfcf565721918ec7355a373911d2f2a227"},{"url":"https://git.kernel.org/stable/c/9221a594c72a1446137926d4c2aa04e345f798dc"},{"url":"https://git.kernel.org/stable/c/66dbb13eeb2fc339f8f548a9076be4c1a94857b0"},{"url":"https://git.kernel.org/stable/c/3a49bbae676fef1ffe548971e6229ae2adeb9d10"},{"url":"https://git.kernel.org/stable/c/90b662ea25f5e83bb3b8ccec5b93ced810b92fb8"}],"tags":["cve.org"],"epss":0.00216,"epssPercentile":0.12151,"ingestedAt":"2026-11-06T18:00:12.565Z","slug":"CVE-2026-74284","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= 72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7 < a425c82ff06cda5165e0de3de8c2a445ec1f863e`\n- `Linux >= a5efc95a33bd4fcb879250852828cc58c7862970 < fc973ecd1a079b9a87c360478542f3a56dea085b`\n- `Linux >= 0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87 < 15720cd8fa3fc625146128f89a8e11b0449a20a7`\n- `Linux >= 9030a91235ae4845ec71902c3e0cecfc9ed1f2df < b2a017bfcf565721918ec7355a373911d2f2a227`\n- `Linux >= d06476714d2819b550e0cc39222347e2c8941c9d < 9221a594c72a1446137926d4c2aa04e345f798dc`\n- `Linux >= 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb < 66dbb13eeb2fc339f8f548a9076be4c1a94857b0`\n- `Linux >= 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb < 3a49bbae676fef1ffe548971e6229ae2adeb9d10`\n- `Linux >= 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb < 90b662ea25f5e83bb3b8ccec5b93ced810b92fb8`\n- `Linux 9a5fd5c2f4d4afdd5e405083ee53e0789ce76956`\n- `Linux c1175c4ad01dbc9c979d099861fa90a754f72059`\n- `Linux >= 5.10.241 < 5.10.261`\n- `Linux >= 5.15.190 < 5.15.212`\n- `Linux >= 6.1.138 < 6.1.178`\n- `Linux >= 6.6.90 < 6.6.145`\n- `Linux >= 6.12.28 < 6.12.97`\n- `Linux >= 5.4.297 < 5.5`\n- `Linux >= 6.14.6 < 6.15`\n- `Linux 6.15`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}