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Linux KernelOperating system · Linux

CVE-2025-38457

MEDIUM · 5.5 CVSS v3.1 Published 2025-07-25
Fix available
A fix is available. Upgrade to 5.4.296 / 5.10.240 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: net/sched: Abort __tc_modify_qdisc if parent class does not exist Lion's patch [1] revealed an ancient bug in the qdisc API. Whenever a user creates/modifies a qdisc specifying as a parent another qdisc, the qdisc API will, during grafting, detect that the user is not trying to attach to a class and reject. However grafting is performed after qdisc_create (and thus the qdiscs' init callback) is executed. In qdiscs that eventually call qdisc_tree_reduce_backlog during init or change (such as fq, hhf, choke, etc), an issue arises. For example, executing the following commands: sudo tc qdisc add dev lo root handle a: htb default 2 sudo tc qdisc add dev lo parent a: handle beef fq Qdiscs such as fq, hhf, choke, etc unconditionally invoke qdisc_tree_reduce_backlog() in their control path init() or change() which then causes a failure to find the child class; however, that does not stop the unconditional invocation of the assumed child qdisc's qlen_notify with a null class. All these qdiscs make the assumption that class is non-null. The solution is ensure that qdisc_leaf() which looks up the parent class, and is invoked prior to qdisc_create(), should return failure on not finding the class. In this patch, we leverage qdisc_leaf to return ERR_PTRs whenever the parentid doesn't correspond to a class, so that we can detect it earlier on and abort before qdisc_create is called. [1] https://lore.kernel.org/netdev/[email protected]/

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.6.20, < 5.4.296>= 5.5, < 5.10.240>= 5.11, < 5.15.189>= 5.16, < 6.1.146>= 6.2, < 6.6.99>= 6.7, < 6.12.39>= 6.13, < 6.15.7= 6.16
Debian LinuxOperating system
Affected:= 11.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.4.296 / 5.10.240 / 5.15.189 or later
Fixed in 5.4.2965.10.2405.15.189
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux kernel 5.4.296, 5.10.240, 5.15.189, or 6.1.146 (depending on which branch you are on)

  1. Identify your current kernel version using `uname -r`
  2. For Debian 11 systems: upgrade kernel to version 5.10.240 or later (e.g., via `apt-get update && apt-get upgrade` or by switching to the Debian LTS kernel)
  3. For other Linux distributions: upgrade to the kernel version that contains the fix commit 23c165dde88eac405eebb59051ea1fe139a45803
  4. For kernel 5.4.x branch: upgrade to 5.4.296 or later
  5. For kernel 5.10.x branch: upgrade to 5.10.240 or later
  6. For kernel 5.15.x branch: upgrade to 5.15.189 or later
  7. For kernel 6.1.x branch: upgrade to 6.1.146 or later
  8. Reboot the system to load the new kernel
Caveat Kernel upgrades may require system reboot and could introduce compatibility issues with custom kernel modules or specific hardware drivers; test in staging first

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-38457 in production — separate from our analysis above.

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