CVE-2026-90050Public exploit

Denial of service via unchecked scheduler quantum

Published Sep 17, 2026 · Updated Sep 17, 2026

Denial of service in Linux 7.3-rc1's fq scheduler allows local users to hang packet scheduling via crafted tc qdisc changes. In net/sched/sch_fq.c, fq_change() accepts a quantum of 1, bypassing fq_init() limits and restoring a small-quantum deficit spin. Reachability requires CONFIG_NET_SCH_FQ=y and CAP_NET_ADMIN, which can be namespace-local through unprivileged user namespaces; the documented consequence is scheduling spin, not data access or code execution.

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

Denial of service in Linux 7.3-rc1's fq scheduler allows local users to hang packet scheduling via crafted tc qdisc changes. In net/sched/sch_fq.c, fq_change() accepts a quantum of 1, bypassing fq_init() limits and restoring a small-quantum deficit spin. Reachability requires CONFIG_NET_SCH_FQ=y and CAP_NET_ADMIN, which can be namespace-local through unprivileged user namespaces; the documented consequence is scheduling spin, not data access or code execution.

The record

CVE
CVE-2026-90050
Published
Sep 17, 2026
Updated
Sep 17, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.001
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=709f34f7c28dc4dd6c40343d101850f11e172312 <094cc07f98dfe70a34e2a1923af17fd29b8cf622
  2. Affected versionversion=7.3-rc1
  3. Affected versionversion=d16dac3925be95ad46e986d4b139c9898b6e227f <a27498d34c3f429fb6db3aa609569f8154afa175
  4. Affected versionversion=e35acd56f244d94355f9ab237c2ecc8fba5e6f04 <72e9387884554f47b03bfd40fb8b2bf52789c68d
  5. Affected versionversion=f6b3e3848a5fca63438984acd6d9eceac80814c1 <798283cd0fe7ba997f67e5a917f14ab40afa8d9f

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=709f34f7c28dc4dd6c40343d101850f11e172312 <094cc07f98dfe70a34e2a1923af17fd29b8cf622; version=7.3-rc1; version=d16dac3925be95ad46e986d4b139c9898b6e227f <a27498d34c3f429fb6db3aa609569f8154afa175; version=e35acd56f244d94355f9ab237c2ecc8fba5e6f04 <72e9387884554f47b03bfd40fb8b2bf52789c68d; version=f6b3e3848a5fca63438984acd6d9eceac80814c1 <798283cd0fe7ba997f67e5a917f14ab40afa8d9f

Published CVSS scores

4.4SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
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 exploitPublished

Weakness, pattern, technique

T1499.001OS Exhaustion Flood

Public exploit references

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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