CVE-2026-90053— net/sched: sch_htb: limit htb_classify inner-class filter hops
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.
以下是该 Linux 内核漏洞描述的中文翻译： 在 Linux 内核中，已解决以下漏洞： net/sched: sch_htb: 限制 htb_classify 内部类过滤器的跳转次数 通过切换到 来跟随每个由过滤器选中的内部类，但从未限制跳转（hops）的数量。如果某个内部类上的过滤器指向自身或指向另一个指回该类的内部类，就会在持有 qdisc 锁且中断（BH）被禁用的情况下，在数据包分类路径中创建无限循环——单个数据包即可导致软死锁/内核恐慌（panic）。 通过跳转计数器限制遍历过程；一旦超过限制，就丢弃数据
Affected Version Matrix 16
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 83bb11805b620c498d6417e0e409f26887981489 |
affected |
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 90a149ab1f8344b7f713e9a838f69fde9e8d2a51 |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 010d05df52cec053bdc67d82c5b61cc4996f3fde |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 8c9611f7ba3ea5594e41bac952363aa0966d3280 |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< e54be9aa503a0297b63aec530fbf760350effd45 |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 872317e84fd019ceffba125e62d31586e3336d41 |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 729c4896ab829169f95915d65edd530325910b37 |
affected | ||
2.6.12 |
affected | ||
| … +8 more rows | |||
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I. Basic Information for CVE-2026-90053
Vulnerability Information
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Vulnerability Title
net/sched: sch_htb: limit htb_classify inner-class filter hops
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
net/sched: sch_htb: limit htb_classify inner-class filter hops
htb_classify() follows each filter-selected inner class by switching
to cl->filter_list, but never bounds the number of hops. A filter on
an inner class can point back to itself or to another inner class that
points back, creating an infinite loop in the packet classification
path with the qdisc lock held and BH disabled — a soft lockup / panic
from a single packet.
Bound the traversal with a hop counter and drop the packet with a
rate-limited warning once the bound is exceeded. The counter is
incremented at the point the inner filter chain is picked up, after the
TC_ACT_* switch has consumed the classifier verdict, so a terminal
TC_ACT_QUEUED/STOLEN/TRAP on the last permitted chain still sets *qerr
to __NET_XMIT_STOLEN and the packet is not charged as a drop by this
qdisc or its parent.
The bound is TC_HTB_MAXDEPTH, taken from HTB's own parameters rather than
from the qdisc hierarchy depth limit. Class levels run from 0 to
TC_HTB_MAXDEPTH - 1, so a traversal that strictly descends in level can
take at most TC_HTB_MAXDEPTH hops. That descent is what a sane
configuration does, but it is assumed here rather than enforced:
htb_find() resolves a classid against every class in the qdisc, so a
filter may equally select a sibling or an ancestor. The normal
root -> inner -> leaf path takes a single hop, so the bound does not
affect legitimate classification.
htb_classify() can now return NULL irrespective of CONFIG_NET_CLS_ACT,
whereas previously every NULL return sat inside that ifdef. The NULL
handler in htb_enqueue() therefore cannot stay conditional either, so
drop the ifdef around it. This matches hfsc_enqueue(), which has always
handled a NULL class unconditionally. Without it, a kernel built
without actions would dereference a NULL class instead of dropping.
Conditions to recreate the bug:
- CONFIG_NET_SCHED, CONFIG_NET_SCH_HTB, CONFIG_NET_CLS_U32,
CONFIG_LOCKUP_DETECTOR.
- Create an HTB qdisc on a device (e.g. lo), add an inner class
1:1 with a leaf child 1:10, install a root u32 filter selecting
1:1, and an inner-class u32 filter on 1:1 also selecting 1:1.
- Send one packet (ping). On the unfixed kernel the classify loop
spins with the qdisc lock held; with softlockup_panic=1 it panics.
- Reachable from unprivileged user via unshare -Urn (CAP_NET_ADMIN).
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
Affected Products
II. Public POCs for CVE-2026-90053
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|---|
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Patches & Fixes for CVE-2026-90053 (6)
Same Patch Batch · Linux · 2026-09-17 · 600 CVEs total
| CVE-2026-90173 | 9.8 CRITICAL | smb: smbdirect: free completion queues with ib_free_cq() |
| CVE-2026-92489 | 9.8 CRITICAL | xfrm: Fix skb double-free in xfrm_dev_direct_output() |
| CVE-2026-90104 | 9.8 CRITICAL | NFSv4.1: zero referring call lists before decoding |
| CVE-2026-90235 | 9.8 CRITICAL | sunrpc: xprtsock: annotate shared socket callbacks with READ_ONCE/WRITE_ONCE |
| CVE-2026-90151 | 9.8 CRITICAL | NFSv4: remove callback IDR entry on client allocation failure |
| CVE-2026-90110 | 9.4 CRITICAL | inetpeer: randomize RB-tree node comparison using SipHash |
| CVE-2026-90414 | 9.1 CRITICAL | IB/isert: reject PDUs declaring more data than was received |
| CVE-2026-90413 | 9.1 CRITICAL | IB/isert: reject login PDUs declaring more data than was received |
| CVE-2026-90230 | 9.1 CRITICAL | nvmet: fix heap out-of-bounds read in nvmet_auth_negotiate() |
| CVE-2026-90381 | 8.8 HIGH | wifi: mt76: fix handling channel context with different bands in mt76_switch_vif_chanctx() |
| CVE-2026-90329 | 8.8 HIGH | HID: synchronize input before cleaning up a failed probe |
| CVE-2026-90162 | 8.8 HIGH | ksmbd: defer publishing granted locks to prevent UAF/double-free race |
| CVE-2026-90357 | 8.8 HIGH | wifi: mt76: mt7915: unlink TWT flow if the MCU rejects the agreement |
| CVE-2026-90367 | 8.8 HIGH | wifi: mt76: mt7996: hold dev->mt76.mutex while disabling tx worker in SER |
| CVE-2026-90371 | 8.8 HIGH | wifi: mt76: fix RXDMAD_C buffer recycling race |
| CVE-2026-93042 | 8.8 HIGH | dmaengine: dw-edma: Terminate all descriptors without callbacks |
| CVE-2026-90425 | 8.8 HIGH | iommu/tegra241-cmdqv: Require exactly one Stream ID for a vSID |
| CVE-2026-90240 | 8.8 HIGH | iommu/vt-d: Flush context cache with correct SID when tearing down aliases |
| CVE-2026-90379 | 8.8 HIGH | wifi: mt76: mt7921: Add PCIe AER handler support to prevent system crash |
| CVE-2026-90256 | 8.8 HIGH | Bluetooth: L2CAP: use proto_lock for l2cap_data to fix l2cap_disconn_ind |
Showing top 20 of 600 CVEs. View all on vendor page → →
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