CVE-2026-90053

Kernel hang via cyclic HTB filter traversal

Published Sep 17, 2026 · Updated Sep 17, 2026

Linux HTB packet classification allows local users to hang the kernel through an infinite loop caused by cyclic class filters. The htb_classify() function in net/sched/sch_htb.c follows filter-selected inner classes without bounding traversal, holding the qdisc lock and disabling bottom halves. Exploitation requires HTB configuration with CAP_NET_ADMIN, obtainable through permitted unprivileged user and network namespaces; one packet triggers a soft lockup, or a kernel panic when softlockup_panic=1.

CVSS severity5.5
Medium
EPSS probability0.21%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Linux HTB packet classification allows local users to hang the kernel through an infinite loop caused by cyclic class filters. The htb_classify() function in net/sched/sch_htb.c follows filter-selected inner classes without bounding traversal, holding the qdisc lock and disabling bottom halves. Exploitation requires HTB configuration with CAP_NET_ADMIN, obtainable through permitted unprivileged user and network namespaces; one packet triggers a soft lockup, or a kernel panic when softlockup_panic=1.

The record

CVE
CVE-2026-90053
Published
Sep 17, 2026
Updated
Sep 17, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <010d05df52cec053bdc67d82c5b61cc4996f3fde
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <729c4896ab829169f95915d65edd530325910b37
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <83bb11805b620c498d6417e0e409f26887981489
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <872317e84fd019ceffba125e62d31586e3336d41
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8c9611f7ba3ea5594e41bac952363aa0966d3280
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <90a149ab1f8344b7f713e9a838f69fde9e8d2a51
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e54be9aa503a0297b63aec530fbf760350effd45
  8. Affected versionversion=2.6.12

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <010d05df52cec053bdc67d82c5b61cc4996f3fde; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <729c4896ab829169f95915d65edd530325910b37; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <83bb11805b620c498d6417e0e409f26887981489; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <872317e84fd019ceffba125e62d31586e3336d41; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8c9611f7ba3ea5594e41bac952363aa0966d3280; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <90a149ab1f8344b7f713e9a838f69fde9e8d2a51; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e54be9aa503a0297b63aec530fbf760350effd45; version=2.6.12

Published CVSS scores

5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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Activity data is delayed. The latest report is Sep 28, 2026.

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No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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