CVE-2025-39766

Kernel warning via incorrect CAKE enqueue status

Published Sep 11, 2025 · Updated Sep 11, 2025

Improper packet handling in Linux kernel branches beginning with 4.19 allows local users to trigger a kernel warning through CAKE qdiscs. When a low buffer limit drops a packet from the same tin and flow, cake_enqueue incorrectly returns NET_XMIT_SUCCESS, so htb_enqueue activates an empty child qdisc. Reachability requires permission to configure HTB and CAKE qdiscs and traffic that exceeds the buffer limit; the disclosed result is a kernel warning.

CVSS severity7.8
High
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper packet handling in Linux kernel branches beginning with 4.19 allows local users to trigger a kernel warning through CAKE qdiscs. When a low buffer limit drops a packet from the same tin and flow, cake_enqueue incorrectly returns NET_XMIT_SUCCESS, so htb_enqueue activates an empty child qdisc. Reachability requires permission to configure HTB and CAKE qdiscs and traffic that exceeds the buffer limit; the disclosed result is a kernel warning.

The record

CVE
CVE-2025-39766
Published
Sep 11, 2025
Updated
Sep 11, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 2025Record 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=046f6fd5daefac7f5abdafb436b30f63bc7c602b <0dacfc5372e314d1219f03e64dde3ab495a5a25e
  2. Affected versionversion=046f6fd5daefac7f5abdafb436b30f63bc7c602b <15de71d06a400f7fdc15bf377a2552b0ec437cf5
  3. Affected versionversion=046f6fd5daefac7f5abdafb436b30f63bc7c602b <62d591dde4defb1333d202410609c4ddeae060b3
  4. Affected versionversion=046f6fd5daefac7f5abdafb436b30f63bc7c602b <710866fc0a64eafcb8bacd91bcb1329eb7e5035f
  5. Affected versionversion=046f6fd5daefac7f5abdafb436b30f63bc7c602b <7689ab22de36f8db19095f6bdf11f28cfde92f5c
  6. Affected versionversion=046f6fd5daefac7f5abdafb436b30f63bc7c602b <aa12ee1c1bd260943fd6ab556d8635811c332eeb
  7. Affected versionversion=046f6fd5daefac7f5abdafb436b30f63bc7c602b <de04ddd2980b48caa8d7e24a7db2742917a8b280
  8. Affected versionversion=046f6fd5daefac7f5abdafb436b30f63bc7c602b <ff57186b2cc39766672c4c0332323933e5faaa88
  9. Affected versionversion=4.19

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=046f6fd5daefac7f5abdafb436b30f63bc7c602b <0dacfc5372e314d1219f03e64dde3ab495a5a25e; version=046f6fd5daefac7f5abdafb436b30f63bc7c602b <15de71d06a400f7fdc15bf377a2552b0ec437cf5; version=046f6fd5daefac7f5abdafb436b30f63bc7c602b <62d591dde4defb1333d202410609c4ddeae060b3; version=046f6fd5daefac7f5abdafb436b30f63bc7c602b <710866fc0a64eafcb8bacd91bcb1329eb7e5035f; version=046f6fd5daefac7f5abdafb436b30f63bc7c602b <7689ab22de36f8db19095f6bdf11f28cfde92f5c; version=046f6fd5daefac7f5abdafb436b30f63bc7c602b <aa12ee1c1bd260943fd6ab556d8635811c332eeb; version=046f6fd5daefac7f5abdafb436b30f63bc7c602b <de04ddd2980b48caa8d7e24a7db2742917a8b280; version=046f6fd5daefac7f5abdafb436b30f63bc7c602b <ff57186b2cc39766672c4c0332323933e5faaa88; version=4.19

Published CVSS scores

7.8UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.3Oracle LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
7.0Amazon LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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