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CVE Record

CVE-2025-38193: net_sched: sch_sfq: reject invalid perturb period

In the Linux kernel, the following vulnerability has been resolved: net_sched: sch_sfq: reject invalid perturb period Gerrard Tai reported that SFQ perturb_period has no range check yet, and this can be used to trigger a race condition fixed in a separate patch. We want to make sure ctl->perturb_period * HZ will not overflow and is positive. tc qd add dev lo root sfq perturb -10 # negative value : error Error: sch_sfq: invalid perturb period. tc qd add dev lo root sfq perturb 1000000000 # too big : error Error: sch_sfq: invalid perturb period. tc qd add dev lo root sfq perturb 2000000 # acceptable value tc -s -d qd sh dev lo qdisc sfq 8005: root refcnt 2 limit 127p quantum 64Kb depth 127 flows 128 divisor 1024 perturb 2000000sec Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Linux’s SFQ traffic scheduler did not reject negative or excessively large perturbation periods. A local, low-privileged attacker able to change this setting could reach a race condition with potential confidentiality, integrity, and availability impact. This is high severity at CVSS 7.8, but the supplied sources do not report active exploitation.

Executive priority

Prioritize shared Linux hosts, multi-user servers, and environments where delegated users can manage traffic control. Treat this as a high-priority local privilege-boundary risk, not a remote exploitation emergency. Confirm distribution backports before relying on upstream version numbers alone.

Technical view

sch_sfq accepted perturb_period values without a range check. Multiplication by HZ could overflow or produce a non-positive result, exposing a race condition addressed separately. Stable-kernel commits validate that the computed period remains positive and does not overflow. The bundle does not identify the separate race-fix commit or fully describe its impact mechanics.

Likely exposure

Exposure is limited to affected Linux kernels where a local, low-privileged user can submit SFQ queue-discipline configuration. Internet reachability alone is insufficient because the CVSS vector is local. The supplied version data spans several kernel branches, but distribution package and backport status require vendor confirmation.

Exploitation context

KEV is false, and no supplied source reports exploitation in the wild. The CVSS vector indicates local access, low complexity, low privileges, and no user interaction. Kernel descriptions show invalid configuration values reach the vulnerable path, but do not establish a weaponized exploit or observed attacks.

Researcher notes

The source connects malformed perturb periods to a race condition fixed by another patch, but does not identify that patch or provide a CWE. Affected-version data is broad and ambiguous without package mapping. Correlate stable commits and distribution advisories before declaring individual builds vulnerable or fixed.

Mitigation direction

  • Install vendor or distribution kernel updates containing the applicable Linux stable fix.
  • Check distribution advisories for the exact kernel package's backport and remediation status.
  • Until updated, limit untrusted local users' ability to modify SFQ traffic-control configuration.

Validation and detection

  • Inventory running kernel versions and identify hosts permitting SFQ queue-discipline configuration.
  • Confirm vendor changelogs or package advisories reference this CVE or an applicable stable commit.
  • After updating, confirm invalid negative and excessively large perturb periods are rejected.
  • Verify the fixed kernel is running after any vendor-required restart.
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-2025-38193 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
11Source 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-2025-38193Attack 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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 5.4.297, 5.10.240, 5.15.186, 6.1.142, 6.6.95, 6.12.35, 6.15.4, 6.16affected
Weakness

CWE details

No CWE listed

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