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CVE Record

CVE-2025-38477: net/sched: sch_qfq: Fix race condition on qfq_aggregate

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_qfq: Fix race condition on qfq_aggregate A race condition can occur when 'agg' is modified in qfq_change_agg (called during qfq_enqueue) while other threads access it concurrently. For example, qfq_dump_class may trigger a NULL dereference, and qfq_delete_class may cause a use-after-free. This patch addresses the issue by: 1. Moved qfq_destroy_class into the critical section. 2. Added sch_tree_lock protection to qfq_dump_class and qfq_dump_class_stats.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in Linux’s QFQ network scheduler can mishandle shared kernel data when operations occur concurrently. The resulting NULL dereference or use-after-free could crash a system or potentially compromise confidentiality, integrity, and availability. Exploitation requires local access with low privileges according to the supplied CVSS vector.

Executive priority

Treat this as a high-priority kernel update for exposed multi-user or untrusted-workload Linux systems. Schedule remediation through normal emergency patch governance, with reboot coordination and verification. Systems without local untrusted users and without reachable QFQ functionality may receive lower operational priority after documented validation.

Technical view

qfq_change_agg can modify qfq_aggregate during qfq_enqueue while class-dump or deletion paths access it concurrently. This can cause a NULL dereference in qfq_dump_class or use-after-free in qfq_delete_class. The cited fix expands critical-section coverage and adds scheduler-tree locking to class and statistics dumps.

Likely exposure

Exposure is limited to Linux systems running an affected kernel where the QFQ scheduler code path can be reached. The CVSS vector indicates local, low-privileged access rather than direct remote exploitation. The supplied affected-version data is irregular, so organizations should map their exact distribution kernel packages against vendor advisories and cited fixes.

Exploitation context

The source bundle does not identify public exploitation, a proof of concept, or inclusion in CISA KEV. Active exploitation should therefore not be assumed. The vulnerability nevertheless has high potential impact because it involves unsafe kernel memory access and requires low attack complexity once prerequisite local access exists.

Researcher notes

The record describes a concurrency flaw but assigns no CWE. Observable failure modes are a NULL dereference and use-after-free involving qfq_aggregate lifecycle and concurrent class operations. Multiple stable-tree commits are supplied, indicating backports across kernel branches. Exact affected and fixed package boundaries require distribution-specific confirmation.

Mitigation direction

  • Inventory running Linux kernels and identify systems using the QFQ scheduler.
  • Apply vendor-supported kernel updates containing the cited stable fix, then reboot into the updated kernel.
  • Prioritize multi-user and untrusted-workload hosts because the CVSS vector requires local low-privileged access.
  • Check distribution advisories for exact fixed package versions; the supplied affected-version list is ambiguous.

Validation and detection

  • Confirm the running kernel, not only installed packages, matches a vendor-fixed release.
  • Verify the applicable vendor package includes one of the cited upstream stable commits.
  • Review traffic-control configuration and workload requirements for QFQ use.
  • Monitor for kernel NULL-dereference, use-after-free, or QFQ-related crash reports after remediation.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2025-38477 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
3ADP providers
12Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-38477Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
siemens-SADPADP container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux462dbc9101acd38e92eda93c0726857517a24bbd, 462dbc9101acd38e92eda93c0726857517a24bbd, 462dbc9101acd38e92eda93c0726857517a24bbd, 462dbc9101acd38e92eda93c0726857517a24bbd, 462dbc9101acd38e92eda93c0726857517a24bbd, 462dbc9101acd38e92eda93c0726857517a24bbd, 462dbc9101acd38e92eda93c0726857517a24bbd, 462dbc9101acd38e92eda93c0726857517a24bbdunaffected
LinuxLinux3.8, 0, 5.4.297, 5.10.241, 5.15.190, 6.1.147, 6.6.100, 6.12.40, 6.15.8, 6.16affected
Weakness

CWE details

No CWE listed

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