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CVE Record

CVE-2026-23105: net/sched: qfq: Use cl_is_active to determine whether class is active in qfq_rm_from_ag

In the Linux kernel, the following vulnerability has been resolved: net/sched: qfq: Use cl_is_active to determine whether class is active in qfq_rm_from_ag This is more of a preventive patch to make the code more consistent and to prevent possible exploits that employ child qlen manipulations on qfq. use cl_is_active instead of relying on the child qdisc's qlen to determine class activation.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This Linux kernel flaw concerns the QFQ network scheduler’s handling of active traffic classes. Manipulating a child queue length could make internal class-state decisions inconsistent, creating possible paths to compromise confidentiality, integrity, or availability. The source describes the change as preventive, so practical exploitability is not demonstrated.

Executive priority

Treat this as a high-priority kernel maintenance issue, especially on shared systems or hosts running untrusted workloads. It does not warrant an exploitation emergency based on current evidence, but the potential impact is broad. Patch through supported vendor channels and track ambiguous package mappings until resolved.

Technical view

The vulnerable logic in qfq_rm_from_ag inferred class activity from the child qdisc’s qlen. Because that value may be manipulated, the stable fix instead uses cl_is_active as the authoritative state indicator. CVSS 3.1 scores it 7.8: local access, low complexity, low privileges, no user interaction, and potentially high impact.

Likely exposure

Potential exposure exists on systems running affected Linux kernel versions with relevant QFQ functionality accessible to a local low-privileged actor. The bundle lists releases beginning with 3.8 and several stable versions, but its version data is ambiguous. Confirm exposure through the operating-system vendor’s kernel and backport mapping.

Exploitation context

No active exploitation is established. The CVE is not listed as KEV in the supplied data, and the kernel description calls this a preventive consistency patch intended to prevent possible exploits. No public proof of concept, observed attacks, or demonstrated impact is identified in the bundle.

Researcher notes

The key invariant is class activity state: child qdisc qlen should not determine whether a QFQ class is active. The source supplies no CWE, reproducer, crash trace, or confirmed exploitation. Researchers should distinguish theoretical qlen manipulation from demonstrated security impact and avoid inferring affected distribution packages solely from upstream version labels.

Mitigation direction

  • Install a vendor-supported kernel update containing the applicable referenced QFQ fix or backport.
  • Use operating-system vendor guidance to map packaged kernel versions to the upstream fix commits.
  • If immediate patching is impossible, check vendor guidance for supported temporary mitigations.
  • Prioritize multi-user or untrusted-workload systems where local low-privileged access is available.

Validation and detection

  • Inventory running kernel versions across hosts, appliances, virtual machines, and container hosts.
  • Confirm whether each packaged kernel includes an applicable referenced stable commit or vendor backport.
  • Identify systems where QFQ scheduling functionality is configured or otherwise available.
  • Reboot after kernel replacement, then verify the updated kernel is actually running.
  • Document uncertain version mappings and resolve them using the relevant distribution’s advisory.
Prepared
Confidence
medium
Sources
9

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.

ATT&CK lookup starting points

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CVE-2026-23105 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
1ADP providers
8Source links

SSVC decision data

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

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-2026-23105Attack 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

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, 462dbc9101acd38e92eda93c0726857517a24bbdunaffected
LinuxLinux3.8, 0, 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.68, 6.18.8, 6.19affected
Weakness

CWE details

No CWE listed

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