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CVE-2025-38457· NVD / CVE Program· CNA Linux

net/sched: Abort __tc_modify_qdisc if parent class does not exist

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/d912cbd7-193b-4269-9857-525bee8bbb6a@gmail.com/

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Jul 25, 2025
Updated
Jul 14, 2026
EPSS
0.2% · 6th percentile
CWE
—
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Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

Affected systems

VendorProduct
linuxlinux kernel
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux11.0
  • linux linux kernel5.5 and later · before 5.10.240
  • linux linux kernel5.11 and later · before 5.15.189
  • linux linux kernel5.16 and later · before 6.1.146
  • linux linux kernel2.6.20 and later · before 5.4.296
  • linux linux kernel6.7 and later · before 6.12.39
  • linux linux kernel6.13 and later · before 6.15.7
  • linux linux kernel6.2 and later · before 6.6.99
  • linux linux kernel6.16

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.20affected
    • 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 and later · before 923a276c74e25073ae391e930792ac86a9f77f1eaffected · git
    • 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 and later · before 90436e72c9622c2f70389070088325a3232d339faffected · git
    • 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 and later · before 25452638f133ac19d75af3f928327d8016952c8eaffected · git
    • 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 and later · before 23c165dde88eac405eebb59051ea1fe139a45803affected · git
    • 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 and later · before 4c691d1b6b6dbd73f30ed9ee7da05f037b0c49afaffected · git
    • 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 and later · before 8ecd651ef24ab50123692a4e3e25db93cb11602aaffected · git
    • 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 and later · before e28a383d6485c3bb51dc5953552f76c4dea33eeaaffected · git
    • 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 and later · before ffdde7bf5a439aaa1955ebd581f5c64ab1533963affected · git
    • before 2.6.20not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.147-16.1.147-1
Debian:13linuxbefore 6.12.41-16.12.41-1
Debian:14linuxbefore 6.16.3-16.16.3-1

Same product

linux: all records

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Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux23c165dde88eac405eebb59051ea1fe139a45803Vendor (CNA)
Linux Linux25452638f133ac19d75af3f928327d8016952c8eVendor (CNA)
Linux Linux4c691d1b6b6dbd73f30ed9ee7da05f037b0c49afVendor (CNA)
Linux Linux8ecd651ef24ab50123692a4e3e25db93cb11602aVendor (CNA)
Linux Linux90436e72c9622c2f70389070088325a3232d339fVendor (CNA)
Linux Linux923a276c74e25073ae391e930792ac86a9f77f1eVendor (CNA)
Linux Linuxe28a383d6485c3bb51dc5953552f76c4dea33eeaVendor (CNA)
Linux Linuxffdde7bf5a439aaa1955ebd581f5c64ab1533963Vendor (CNA)
azl3 kernel 6.6.96.2-2 on Azure Linux 3.06.6.104.2-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 kernel 5.15.186.1-1 on CBL Mariner 2.05.15.200.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.147-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Noroxi analysis

No Noroxi analysis for this record yet

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Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records