CVE-2026-74284

Traffic stall via duplicate HFSC passive transition

Published Aug 15, 2026 · Updated Aug 15, 2026

Denial of service in the Linux kernel HFSC scheduler allows local users to stall queued traffic through a crafted class hierarchy. The update_vf() path arms go_passive after hfsc_qlen_notify() has already made the empty child passive, so the stale flag decrements its parent's cl_nactive twice and removes that parent from the vttree. Reaching the flaw requires an HFSC hierarchy whose child qdisc drops its final packets during dequeue; backlogged sibling classes then stop transmitting indefinitely.

CVSS severity5.5
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the Linux kernel HFSC scheduler allows local users to stall queued traffic through a crafted class hierarchy. The update_vf() path arms go_passive after hfsc_qlen_notify() has already made the empty child passive, so the stale flag decrements its parent's cl_nactive twice and removes that parent from the vttree. Reaching the flaw requires an HFSC hierarchy whose child qdisc drops its final packets during dequeue; backlogged sibling classes then stop transmitting indefinitely.

The record

CVE
CVE-2026-74284
Published
Aug 15, 2026
Updated
Aug 15, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-821, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 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=0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87 <15720cd8fa3fc625146128f89a8e11b0449a20a7
  2. Affected versionversion=5.10.241 <5.10.261
  3. Affected versionversion=5.15.190 <5.15.212
  4. Affected versionversion=51eb3b65544c9efd6a1026889ee5fb5aa62da3bb <3a49bbae676fef1ffe548971e6229ae2adeb9d10
  5. Affected versionversion=51eb3b65544c9efd6a1026889ee5fb5aa62da3bb <66dbb13eeb2fc339f8f548a9076be4c1a94857b0
  6. Affected versionversion=51eb3b65544c9efd6a1026889ee5fb5aa62da3bb <90b662ea25f5e83bb3b8ccec5b93ced810b92fb8
  7. Affected versionversion=5.4.297 <5.5
  8. Affected versionversion=6.1.138 <6.1.178
  9. Affected versionversion=6.12.28 <6.12.97
  10. Affected versionversion=6.14.6 <6.15
  11. Affected versionversion=6.15
  12. Affected versionversion=6.6.90 <6.6.145
  13. Affected versionversion=72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7 <a425c82ff06cda5165e0de3de8c2a445ec1f863e
  14. Affected versionversion=9030a91235ae4845ec71902c3e0cecfc9ed1f2df <b2a017bfcf565721918ec7355a373911d2f2a227
  15. Affected versionversion=9a5fd5c2f4d4afdd5e405083ee53e0789ce76956
  16. Affected versionversion=a5efc95a33bd4fcb879250852828cc58c7862970 <fc973ecd1a079b9a87c360478542f3a56dea085b
  17. Affected versionversion=c1175c4ad01dbc9c979d099861fa90a754f72059
  18. Affected versionversion=d06476714d2819b550e0cc39222347e2c8941c9d <9221a594c72a1446137926d4c2aa04e345f798dc

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87 <15720cd8fa3fc625146128f89a8e11b0449a20a7; version=5.10.241 <5.10.261; version=5.15.190 <5.15.212; version=51eb3b65544c9efd6a1026889ee5fb5aa62da3bb <3a49bbae676fef1ffe548971e6229ae2adeb9d10; version=51eb3b65544c9efd6a1026889ee5fb5aa62da3bb <66dbb13eeb2fc339f8f548a9076be4c1a94857b0; version=51eb3b65544c9efd6a1026889ee5fb5aa62da3bb <90b662ea25f5e83bb3b8ccec5b93ced810b92fb8; version=5.4.297 <5.5; version=6.1.138 <6.1.178; version=6.12.28 <6.12.97; version=6.14.6 <6.15; version=6.15; version=6.6.90 <6.6.145; version=72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7 <a425c82ff06cda5165e0de3de8c2a445ec1f863e; version=9030a91235ae4845ec71902c3e0cecfc9ed1f2df <b2a017bfcf565721918ec7355a373911d2f2a227; version=9a5fd5c2f4d4afdd5e405083ee53e0789ce76956; version=a5efc95a33bd4fcb879250852828cc58c7862970 <fc973ecd1a079b9a87c360478542f3a56dea085b; version=c1175c4ad01dbc9c979d099861fa90a754f72059; version=d06476714d2819b550e0cc39222347e2c8941c9d <9221a594c72a1446137926d4c2aa04e345f798dc

Published CVSS scores

5.5Oracle 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

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

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-821Incorrect Synchronization
T1499.004Endpoint Denial of Service: Application 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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