{"id":"CVE-2026-74284","state":"PUBLISHED","title":"net/sched: sch_hfsc: Don't make class passive twice","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.","publishedAt":"2026-08-15T05:57:53.290Z","updatedAt":"2026-08-17T05:16:29.785Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7","status":"affected","lessThan":"a425c82ff06cda5165e0de3de8c2a445ec1f863e","versionType":"git"},{"version":"a5efc95a33bd4fcb879250852828cc58c7862970","status":"affected","lessThan":"fc973ecd1a079b9a87c360478542f3a56dea085b","versionType":"git"},{"version":"0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87","status":"affected","lessThan":"15720cd8fa3fc625146128f89a8e11b0449a20a7","versionType":"git"},{"version":"9030a91235ae4845ec71902c3e0cecfc9ed1f2df","status":"affected","lessThan":"b2a017bfcf565721918ec7355a373911d2f2a227","versionType":"git"},{"version":"d06476714d2819b550e0cc39222347e2c8941c9d","status":"affected","lessThan":"9221a594c72a1446137926d4c2aa04e345f798dc","versionType":"git"},{"version":"51eb3b65544c9efd6a1026889ee5fb5aa62da3bb","status":"affected","lessThan":"66dbb13eeb2fc339f8f548a9076be4c1a94857b0","versionType":"git"},{"version":"51eb3b65544c9efd6a1026889ee5fb5aa62da3bb","status":"affected","lessThan":"3a49bbae676fef1ffe548971e6229ae2adeb9d10","versionType":"git"},{"version":"51eb3b65544c9efd6a1026889ee5fb5aa62da3bb","status":"affected","lessThan":"90b662ea25f5e83bb3b8ccec5b93ced810b92fb8","versionType":"git"},{"version":"9a5fd5c2f4d4afdd5e405083ee53e0789ce76956","status":"affected","versionType":"git"},{"version":"c1175c4ad01dbc9c979d099861fa90a754f72059","status":"affected","versionType":"git"},{"version":"5.10.241","status":"affected","lessThan":"5.10.261","versionType":"semver"},{"version":"5.15.190","status":"affected","lessThan":"5.15.212","versionType":"semver"},{"version":"6.1.138","status":"affected","lessThan":"6.1.178","versionType":"semver"},{"version":"6.6.90","status":"affected","lessThan":"6.6.145","versionType":"semver"},{"version":"6.12.28","status":"affected","lessThan":"6.12.97","versionType":"semver"},{"version":"5.4.297","status":"affected","lessThan":"5.5","versionType":"semver"},{"version":"6.14.6","status":"affected","lessThan":"6.15","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_hfsc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_hfsc.c"]}],"references":["https://git.kernel.org/stable/c/a425c82ff06cda5165e0de3de8c2a445ec1f863e","https://git.kernel.org/stable/c/fc973ecd1a079b9a87c360478542f3a56dea085b","https://git.kernel.org/stable/c/15720cd8fa3fc625146128f89a8e11b0449a20a7","https://git.kernel.org/stable/c/b2a017bfcf565721918ec7355a373911d2f2a227","https://git.kernel.org/stable/c/9221a594c72a1446137926d4c2aa04e345f798dc","https://git.kernel.org/stable/c/66dbb13eeb2fc339f8f548a9076be4c1a94857b0","https://git.kernel.org/stable/c/3a49bbae676fef1ffe548971e6229ae2adeb9d10","https://git.kernel.org/stable/c/90b662ea25f5e83bb3b8ccec5b93ced810b92fb8"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74284.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74284","state":"PUBLISHED","datePublished":"2026-08-15T05:57:53.290Z","dateUpdated":"2026-08-17T05:16:29.785Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.881Z"},"containers":{"cna":{"title":"net/sched: sch_hfsc: Don't make class passive twice","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7","status":"affected","lessThan":"a425c82ff06cda5165e0de3de8c2a445ec1f863e","versionType":"git"},{"version":"a5efc95a33bd4fcb879250852828cc58c7862970","status":"affected","lessThan":"fc973ecd1a079b9a87c360478542f3a56dea085b","versionType":"git"},{"version":"0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87","status":"affected","lessThan":"15720cd8fa3fc625146128f89a8e11b0449a20a7","versionType":"git"},{"version":"9030a91235ae4845ec71902c3e0cecfc9ed1f2df","status":"affected","lessThan":"b2a017bfcf565721918ec7355a373911d2f2a227","versionType":"git"},{"version":"d06476714d2819b550e0cc39222347e2c8941c9d","status":"affected","lessThan":"9221a594c72a1446137926d4c2aa04e345f798dc","versionType":"git"},{"version":"51eb3b65544c9efd6a1026889ee5fb5aa62da3bb","status":"affected","lessThan":"66dbb13eeb2fc339f8f548a9076be4c1a94857b0","versionType":"git"},{"version":"51eb3b65544c9efd6a1026889ee5fb5aa62da3bb","status":"affected","lessThan":"3a49bbae676fef1ffe548971e6229ae2adeb9d10","versionType":"git"},{"version":"51eb3b65544c9efd6a1026889ee5fb5aa62da3bb","status":"affected","lessThan":"90b662ea25f5e83bb3b8ccec5b93ced810b92fb8","versionType":"git"},{"version":"9a5fd5c2f4d4afdd5e405083ee53e0789ce76956","status":"affected","versionType":"git"},{"version":"c1175c4ad01dbc9c979d099861fa90a754f72059","status":"affected","versionType":"git"},{"version":"5.10.241","status":"affected","lessThan":"5.10.261","versionType":"semver"},{"version":"5.15.190","status":"affected","lessThan":"5.15.212","versionType":"semver"},{"version":"6.1.138","status":"affected","lessThan":"6.1.178","versionType":"semver"},{"version":"6.6.90","status":"affected","lessThan":"6.6.145","versionType":"semver"},{"version":"6.12.28","status":"affected","lessThan":"6.12.97","versionType":"semver"},{"version":"5.4.297","status":"affected","lessThan":"5.5","versionType":"semver"},{"version":"6.14.6","status":"affected","lessThan":"6.15","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_hfsc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_hfsc.c"]}],"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"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:16:29.785Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.241","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.190","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.138","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.90","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.28","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.297"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14.6"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}