Incorrect Synchronization Affecting kernel6.18-tools-devel package, versions <1:6.18.41-94.142.amzn2023
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-AMZN2023-KERNEL618TOOLSDEVEL-19467975
- published1 Sept 2026
- disclosed15 Aug 2026
Introduced: 15 Aug 2026
NewCVE-2026-74284 (opens in a new tab)How to fix?
Upgrade Amazon-Linux:2023 kernel6.18-tools-devel to version 1:6.18.41-94.142.amzn2023 or higher.
This issue was patched in ALAS2023-2026-2071.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel6.18-tools-devel package and not the kernel6.18-tools-devel package as distributed by Amazon-Linux.
See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.
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:
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).
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.
References
- http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-74284
- 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