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CVE Record

CVE-2026-22999: net/sched: sch_qfq: do not free existing class in qfq_change_class()

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_qfq: do not free existing class in qfq_change_class() Fixes qfq_change_class() error case. cl->qdisc and cl should only be freed if a new class and qdisc were allocated, or we risk various UAF.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This is a high-severity Linux kernel memory safety flaw in the QFQ network scheduler. A local low-privileged actor could potentially trigger use-after-free behavior, risking system compromise or crash. The supplied sources do not show remote exposure or confirmed exploitation.

Executive priority

Treat as a priority kernel update for systems with local users or untrusted workloads. It is high impact, but the supplied evidence does not support emergency remote-exploitation treatment.

Technical view

The fix prevents qfq_change_class() from freeing an existing class and qdisc on an error path. Freeing objects that were not newly allocated could create use-after-free conditions in net/sched sch_qfq. CVSS is 7.8: local attack vector, low complexity, low privileges, no user interaction, high confidentiality, integrity, and availability impact.

Likely exposure

Linux systems running affected kernel ranges and exposing the QFQ scheduler code path are the concern. Exposure is primarily local, especially on multi-user systems, container hosts, or environments running untrusted local workloads.

Exploitation context

The source bundle marks KEV as false and provides no evidence of active exploitation. The CVSS vector indicates local, low-privilege exploitation potential, not a remote network attack.

Researcher notes

Analysis is limited to the CVE record and Linux stable commit references. The bundle does not provide a CWE, exploit details, distribution-specific package status, or operational mitigations beyond applying fixed kernel updates.

Mitigation direction

  • Update Linux kernels to vendor builds containing the referenced stable fixes.
  • Prioritize multi-user, container, and untrusted-workload Linux hosts.
  • Check distribution advisories for exact package versions and backports.
  • If patching is delayed, follow vendor guidance for temporary risk reduction.

Validation and detection

  • Inventory Linux kernel versions across affected fleets.
  • Map installed kernels to vendor-fixed packages or referenced stable commits.
  • Identify systems where QFQ scheduling is available or configured.
  • Review vendor advisories for backported fixes not obvious from version strings.
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-2026-22999 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
0ADP providers
8Source links

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-2026-22999Attack 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.

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, 6.12.67, 6.18.7, 6.19affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.