CVE-2025-39766

HIGH EPSS 6.5%
Published Sep 11, 20259mo ago · Modified Jun 17, 20261w ago
7.8 CVSS 3.1
High
Find Similar
Published Sep 11, 2025 9mo ago
Last Modified Jun 17, 2026 1w ago

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit The following setup can trigger a WARNING in htb_activate due to the condition: !cl->leaf.q->q.qlen tc qdisc del dev lo root tc qdisc add dev lo root handle 1: htb default 1 tc class add dev lo parent 1: classid 1:1 \ htb rate 64bit tc qdisc add dev lo parent 1:1 handle f: \ cake memlimit 1b ping -I lo -f -c1 -s64 -W0.001 127.0.0.1 This is because the low memlimit leads to a low buffer_limit, which causes packet dropping. However, cake_enqueue still returns NET_XMIT_SUCCESS, causing htb_enqueue to call htb_activate with an empty child qdisc. We should return NET_XMIT_CN when packets are dropped from the same tin and flow. I do not believe return value of NET_XMIT_CN is necessary for packet drops in the case of ack filtering, as that is meant to optimize performance, not to signal congestion.

CVSS Details

Base Score
7.8
Exploitability
1.8
Impact
5.9
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality High
Integrity High
Availability High

Threat Intelligence

EPSS Exploit Probability
6.5% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Affected Products 10

VendorProductVersionRange
linuxlinux_kernel*≥4.19  –  <5.4.297
linuxlinux_kernel*≥5.5  –  <5.10.241
linuxlinux_kernel*≥5.11  –  <5.15.190
linuxlinux_kernel*≥5.16  –  <6.1.149
linuxlinux_kernel*≥6.2  –  <6.6.103
linuxlinux_kernel*≥6.7  –  <6.12.44
linuxlinux_kernel*≥6.13  –  <6.16.4
linuxlinux_kernel6.17any
linuxlinux_kernel6.17any
debiandebian_linux11.0any

References 11

  • cert-portal.siemens.com https://cert-portal.siemens.com/productcert/html/ssa-032379.html
  • git.kernel.org https://git.kernel.org/stable/c/0dacfc5372e314d1219f03e64dde3ab495a5a25e
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/15de71d06a400f7fdc15bf377a2552b0ec437cf5
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/62d591dde4defb1333d202410609c4ddeae060b3
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/710866fc0a64eafcb8bacd91bcb1329eb7e5035f
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/7689ab22de36f8db19095f6bdf11f28cfde92f5c
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/aa12ee1c1bd260943fd6ab556d8635811c332eeb
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/de04ddd2980b48caa8d7e24a7db2742917a8b280
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/ff57186b2cc39766672c4c0332323933e5faaa88
    Patch
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
    Mailing ListThird Party Advisory
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
    Mailing ListThird Party Advisory

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/0dacfc5372e314d1219f03e64dde3ab495a5a25e
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/15de71d06a400f7fdc15bf377a2552b0ec437cf5
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/62d591dde4defb1333d202410609c4ddeae060b3
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/710866fc0a64eafcb8bacd91bcb1329eb7e5035f
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/7689ab22de36f8db19095f6bdf11f28cfde92f5c
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/aa12ee1c1bd260943fd6ab556d8635811c332eeb
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/de04ddd2980b48caa8d7e24a7db2742917a8b280
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/ff57186b2cc39766672c4c0332323933e5faaa88
    Patch