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CVE-2026-74284— net/sched: sch_hfsc: Don't make class passive twice

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于net/sched/sch_hfsc在出队时对类被动状态处理不当，可能导致网络队列停滞。

AI Predicted 5.9 Difficulty: Moderate EPSS 0.21% · P11

Affected Version Matrix 27

VendorProduct Version RangeStatus
Linux Linux 72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7< a425c82ff06cda5165e0de3de8c2a445ec1f863e affected
a5efc95a33bd4fcb879250852828cc58c7862970< fc973ecd1a079b9a87c360478542f3a56dea085b affected
0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87< 15720cd8fa3fc625146128f89a8e11b0449a20a7 affected
9030a91235ae4845ec71902c3e0cecfc9ed1f2df< b2a017bfcf565721918ec7355a373911d2f2a227 affected
d06476714d2819b550e0cc39222347e2c8941c9d< 9221a594c72a1446137926d4c2aa04e345f798dc affected
51eb3b65544c9efd6a1026889ee5fb5aa62da3bb< 66dbb13eeb2fc339f8f548a9076be4c1a94857b0 affected
51eb3b65544c9efd6a1026889ee5fb5aa62da3bb< 3a49bbae676fef1ffe548971e6229ae2adeb9d10 affected
51eb3b65544c9efd6a1026889ee5fb5aa62da3bb< 90b662ea25f5e83bb3b8ccec5b93ced810b92fb8 affected
… +19 more rows
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I. Basic Information for CVE-2026-74284

Vulnerability Information
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Vulnerability Title
net/sched: sch_hfsc: Don't make class passive twice
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于net/sched/sch_hfsc在出队时对类被动状态处理不当，可能导致网络队列停滞。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7 ~ a425c82ff06cda5165e0de3de8c2a445ec1f863e -
Linux Linux 6.15 -

II. Public POCs for CVE-2026-74284

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III. Intelligence Information for CVE-2026-74284

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Patches & Fixes for CVE-2026-74284 (8)

Same Patch Batch · Linux · 2026-08-15 · 845 CVEs total

CVE-2026-74280 10.0 CRITICAL crypto: marvell/octeontx - fix DMA cleanup using wrong loop index
CVE-2026-74279 10.0 CRITICAL crypto: cavium/cpt - fix DMA cleanup using wrong loop index
CVE-2026-74475 10.0 CRITICAL vxlan: use neigh_ha_snapshot() in route_shortcircuit()
CVE-2026-72407 10.0 CRITICAL geneve: validate inner network offset in geneve_gro_complete()
CVE-2026-74309 10.0 CRITICAL vdpa/octeon_ep: fix IRQ-to-ring mapping in interrupt handler
CVE-2026-72408 10.0 CRITICAL geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
CVE-2026-72421 10.0 CRITICAL ipv4: fib: Don't ignore error route in local/main tables.
CVE-2026-72493 9.9 CRITICAL net: serialize netif_running() check in enqueue_to_backlog()
CVE-2026-72463 9.8 CRITICAL xfrm: Fix dev use-after-free in xfrm async resumption
CVE-2026-72248 9.8 CRITICAL netfilter: flowtable: support IPIP tunnel with direct xmit
CVE-2026-72477 9.8 CRITICAL fs/ntfs3: call _ntfs_bad_inode() when failing to rename
CVE-2026-72381 9.8 CRITICAL ksmbd: fix use-after-free of fp->owner.name in durable handle owner check
CVE-2026-72473 9.8 CRITICAL xprtrdma: Decouple req recycling from RPC completion
CVE-2026-72472 9.8 CRITICAL nfs: use nfsi->rwsem to protect traversal of the file lock list
CVE-2026-74406 9.8 CRITICAL vxlan: Fix potential null-ptr-deref in vxlan_gro_prepare_receive().
CVE-2026-72139 9.8 CRITICAL tcp: defer md5sig_info kfree past RCU grace period in tcp_connect
CVE-2026-74401 9.8 CRITICAL dlm: fix add msg handle in send_queue ordered
CVE-2026-72137 9.8 CRITICAL xfrm: nat_keepalive: avoid double free on send error
CVE-2026-74376 9.8 CRITICAL md/raid10: reset read_slot when reusing r10bio for discard
CVE-2026-72130 9.8 CRITICAL nvmet-auth: reject short AUTH_RECEIVE buffers

Showing top 20 of 845 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-74284

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