CVE-2026-74284
Estado: RecibidaSin puntuar—
In the Linux kernel, the following vulnerability has been resolved:
net/sched: sch_hfsc: Don't make class passive twice
update_vf() is called from two places for the same class during a single dequeue when the class's child qdisc (e.g. codel/fq_codel) drops its last packets while dequeuing:
On the second call the class is already passive, but its child qdisc is still empty, so update_vf() arms go_passive again:
The leaf is then skipped by the cl_nactive == 0 check inside the loop, which does not clear go_passive, so the stale go_passive propagates to the parent and decrements its cl_nactive a second time.
Leer descripción completaMostrar menos
A parent that still has other active children is driven to cl_nactive == 0 and removed from the vttree, even though those siblings are still backlogged. They are never dequeued again and the qdisc stalls.
Fix this by only arming go_passive when the class is actually active, so an already-passive class no longer triggers a second passive transition. The byte accounting (cl->cl_total += len) still runs for every ancestor, so dequeued bytes continue to be counted exactly once.
Detalles técnicos trazas, registros y código del informe original
1. The child calls qdisc_tree_reduce_backlog(), which, now that the child
is empty, invokes hfsc_qlen_notify() -> update_vf(cl, 0, 0) and turns
the class passive (cl_nactive is decremented up the hierarchy).
2. hfsc_dequeue() then calls update_vf(cl, qdisc_pkt_len(skb), cur_time)
to charge the dequeued bytes.
if (cl->qdisc->q.qlen == 0 && cl->cl_flags & HFSC_FSC)
go_passive = 1;CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.22%
- Percentil entre todas las CVEs puntuadas: 11
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
- 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
- https://git.kernel.org/stable/c/a425c82ff06cda5165e0de3de8c2a445ec1f863e
- https://git.kernel.org/stable/c/b2a017bfcf565721918ec7355a373911d2f2a227
- https://git.kernel.org/stable/c/fc973ecd1a079b9a87c360478542f3a56dea085b
JSON original (NVD)
Mostrar
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"id": "CVE-2026-74284",
"cveTags": [],
"metrics": {},
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{
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}
],
"published": "2026-08-15T06:22:27.903",
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{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"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."
}
],
"lastModified": "2026-08-17T06:19:22.257",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}