CVE-2025-38350

HIGH EPSS 7.8%
Published Jul 19, 202511mo ago · Modified Jun 17, 20261w ago
7.8 CVSS 3.1
High
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Published Jul 19, 2025 11mo ago
Last Modified Jun 17, 2026 1w ago

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: Always pass notifications when child class becomes empty Certain classful qdiscs may invoke their classes' dequeue handler on an enqueue operation. This may unexpectedly empty the child qdisc and thus make an in-flight class passive via qlen_notify(). Most qdiscs do not expect such behaviour at this point in time and may re-activate the class eventually anyways which will lead to a use-after-free. The referenced fix commit attempted to fix this behavior for the HFSC case by moving the backlog accounting around, though this turned out to be incomplete since the parent's parent may run into the issue too. The following reproducer demonstrates this use-after-free: tc qdisc add dev lo root handle 1: drr tc filter add dev lo parent 1: basic classid 1:1 tc class add dev lo parent 1: classid 1:1 drr tc qdisc add dev lo parent 1:1 handle 2: hfsc def 1 tc class add dev lo parent 2: classid 2:1 hfsc rt m1 8 d 1 m2 0 tc qdisc add dev lo parent 2:1 handle 3: netem tc qdisc add dev lo parent 3:1 handle 4: blackhole echo 1 | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888 tc class delete dev lo classid 1:1 echo 1 | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888 Since backlog accounting issues leading to a use-after-frees on stale class pointers is a recurring pattern at this point, this patch takes a different approach. Instead of trying to fix the accounting, the patch ensures that qdisc_tree_reduce_backlog always calls qlen_notify when the child qdisc is empty. This solves the problem because deletion of qdiscs always involves a call to qdisc_reset() and / or qdisc_purge_queue() which ultimately resets its qlen to 0 thus causing the following qdisc_tree_reduce_backlog() to report to the parent. Note that this may call qlen_notify on passive classes multiple times. This is not a problem after the recent patch series that made all the classful qdiscs qlen_notify() handlers idempotent.

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
7.8% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-416 Use After Free Memory Safety

Affected Products 14

VendorProductVersionRange
linuxlinux_kernel*≥5.4.294  –  <5.4.296
linuxlinux_kernel*≥5.10.238  –  <5.10.240
linuxlinux_kernel*≥5.15.185  –  <5.15.187
linuxlinux_kernel*≥6.1.141  –  <6.1.144
linuxlinux_kernel*≥6.6.93  –  <6.6.97
linuxlinux_kernel*≥6.12.31  –  <6.12.37
linuxlinux_kernel*≥6.14.9  –  <6.15
linuxlinux_kernel*≥6.15.1  –  <6.15.6
linuxlinux_kernel6.15any
linuxlinux_kernel6.16any
linuxlinux_kernel6.16any
linuxlinux_kernel6.16any
linuxlinux_kernel6.16any
debiandebian_linux11.0any

References 12

  • cert-portal.siemens.com https://cert-portal.siemens.com/productcert/html/ssa-082556.html
  • cert-portal.siemens.com https://cert-portal.siemens.com/productcert/html/ssa-089022.html
  • git.kernel.org https://git.kernel.org/stable/c/103406b38c600fec1fe375a77b27d87e314aea09
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/3b290923ad2b23596208c1e29520badef4356a43
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/7874c9c132e906a52a187d045995b115973c93fb
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/a44acdd9e84a211989ff4b9b92bf3545d8456ad5
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/a553afd91f55ff39b1e8a1c4989a29394c9e0472
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/e269f29e9395527bc00c213c6b15da04ebb35070
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/e9921b57dca05ac5f4fa1fa8e993d4f0ee52e2b7
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/f680a4643c6f71e758d8fe0431a958e9a6a4f59d
    Patch
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
    Third Party Advisory
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
    Third Party Advisory

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/103406b38c600fec1fe375a77b27d87e314aea09
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/3b290923ad2b23596208c1e29520badef4356a43
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/7874c9c132e906a52a187d045995b115973c93fb
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/a44acdd9e84a211989ff4b9b92bf3545d8456ad5
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/a553afd91f55ff39b1e8a1c4989a29394c9e0472
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/e269f29e9395527bc00c213c6b15da04ebb35070
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/e9921b57dca05ac5f4fa1fa8e993d4f0ee52e2b7
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/f680a4643c6f71e758d8fe0431a958e9a6a4f59d
    Patch