CVE-2026-90073

Local denial of service via scheduler quantum overflow

Published Sep 17, 2026 · Updated Sep 17, 2026

Integer overflow in Linux's HHF scheduler allows local users to hang packet dequeuing through an oversized network-device MTU. In net/sched/sch_hhf.c, hhf_init() derives an unchecked quantum from the device MTU, allowing weight multiplied by quantum to overflow the signed deficit in hhf_dequeue() and loop indefinitely. Exploitation requires CAP_NET_ADMIN in a user namespace and an MTU plus link-layer header length that reaches the sign bit; the documented consequence is a scheduler hang.

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

Integer overflow in Linux's HHF scheduler allows local users to hang packet dequeuing through an oversized network-device MTU. In net/sched/sch_hhf.c, hhf_init() derives an unchecked quantum from the device MTU, allowing weight multiplied by quantum to overflow the signed deficit in hhf_dequeue() and loop indefinitely. Exploitation requires CAP_NET_ADMIN in a user namespace and an MTU plus link-layer header length that reaches the sign bit; the documented consequence is a scheduler hang.

The record

CVE
CVE-2026-90073
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=10239edf86f137ce4c39b62ea9575e8053c549a0 <0c66223e90ddb4fd3700965a9241f2fde7bd6bc7
  2. Affected versionversion=10239edf86f137ce4c39b62ea9575e8053c549a0 <20b65bf7ca06e48ec1d62ed8012f71205328dbe4
  3. Affected versionversion=10239edf86f137ce4c39b62ea9575e8053c549a0 <2164b512b97bb053e8ce4d6e95576f11bed6a005
  4. Affected versionversion=10239edf86f137ce4c39b62ea9575e8053c549a0 <2446644b0f6d045b01db6acbaf55552dbec8a59a
  5. Affected versionversion=10239edf86f137ce4c39b62ea9575e8053c549a0 <2e0f0729f922c8de13801004e2131b57646c7c5f
  6. Affected versionversion=10239edf86f137ce4c39b62ea9575e8053c549a0 <99770b5d8e0e1c69b996f74a19d71afd2c4a9aa4
  7. Affected versionversion=10239edf86f137ce4c39b62ea9575e8053c549a0 <dea2789a9d5ff38bdd77f2e64d550430899e2839
  8. Affected versionversion=10239edf86f137ce4c39b62ea9575e8053c549a0 <fa9c2055f0a60f801ccf286af53d387dc6202c3f
  9. Affected versionversion=3.14

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=10239edf86f137ce4c39b62ea9575e8053c549a0 <0c66223e90ddb4fd3700965a9241f2fde7bd6bc7; version=10239edf86f137ce4c39b62ea9575e8053c549a0 <20b65bf7ca06e48ec1d62ed8012f71205328dbe4; version=10239edf86f137ce4c39b62ea9575e8053c549a0 <2164b512b97bb053e8ce4d6e95576f11bed6a005; version=10239edf86f137ce4c39b62ea9575e8053c549a0 <2446644b0f6d045b01db6acbaf55552dbec8a59a; version=10239edf86f137ce4c39b62ea9575e8053c549a0 <2e0f0729f922c8de13801004e2131b57646c7c5f; version=10239edf86f137ce4c39b62ea9575e8053c549a0 <99770b5d8e0e1c69b996f74a19d71afd2c4a9aa4; version=10239edf86f137ce4c39b62ea9575e8053c549a0 <dea2789a9d5ff38bdd77f2e64d550430899e2839; version=10239edf86f137ce4c39b62ea9575e8053c549a0 <fa9c2055f0a60f801ccf286af53d387dc6202c3f; version=3.14

Published CVSS scores

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

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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