CVE-2026-74284

Description

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: 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. On the second call the class is already passive, but its child qdisc is still empty, so update_vf() arms go_passive again: if (cl->qdisc->q.qlen == 0 && cl->cl_flags & HFSC_FSC) go_passive = 1; 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. 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.

Gravité et risque d'exploitation

CVE-2026-74284 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.22 %, ce qui la place devant 11.3 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, 7.1.5, 6.18.40, <=6.12.*, 7.2, 6.6.90, c1175c4ad01dbc9c979d099861fa90a754f72059, 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb, <15720cd8fa3fc625146128f89a8e11b0449a20a7, <5.15.212, 0, <=7.1.*, 9a5fd5c2f4d4afdd5e405083ee53e0789ce76956, <9221a594c72a1446137926d4c2aa04e345f798dc, 5.4.297, <a425c82ff06cda5165e0de3de8c2a445ec1f863e, 6.1.178, <=5.10.*, d06476714d2819b550e0cc39222347e2c8941c9d, <=6.6.*, <66dbb13eeb2fc339f8f548a9076be4c1a94857b0, <6.1.178, 6.12.97, 5.15.190, 6.1.138, 0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87, <5.5, <=6.18.*, 6.14.6, 5.15.212, a5efc95a33bd4fcb879250852828cc58c7862970, 6.6.145, 5.10.261, 6.15, <5.10.261, <3a49bbae676fef1ffe548971e6229ae2adeb9d10, <6.6.145, 5.10.241, <=*, <=5.15.*, <90b662ea25f5e83bb3b8ccec5b93ced810b92fb8, <6.15, <b2a017bfcf565721918ec7355a373911d2f2a227, 72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7, <6.12.97, 9030a91235ae4845ec71902c3e0cecfc9ed1f2df, <fc973ecd1a079b9a87c360478542f3a56dea085b, 6.12.28) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• 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