LiveActive security incident?Get immediate response
CVE Record

CVE-2025-38177: sch_hfsc: make hfsc_qlen_notify() idempotent

In the Linux kernel, the following vulnerability has been resolved: sch_hfsc: make hfsc_qlen_notify() idempotent hfsc_qlen_notify() is not idempotent either and not friendly to its callers, like fq_codel_dequeue(). Let's make it idempotent to ease qdisc_tree_reduce_backlog() callers' life: 1. update_vf() decreases cl->cl_nactive, so we can check whether it is non-zero before calling it. 2. eltree_remove() always removes RB node cl->el_node, but we can use RB_EMPTY_NODE() + RB_CLEAR_NODE() to make it safe.

HighCVSS 7.8Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel flaw in the HFSC network traffic scheduler can mishandle repeated queue-length notifications. The supplied CVSS assessment indicates a low-privileged local attacker could potentially cause serious confidentiality, integrity, and availability impacts. Exposure depends on the running kernel and whether the affected scheduler path is reachable.

Executive priority

Prioritize remediation on multi-user or otherwise locally accessible Linux systems, especially where HFSC is used. This is high severity, but the supplied evidence does not establish remote reachability or active exploitation. Use normal expedited kernel-patching procedures rather than emergency internet-facing incident response unless separate evidence changes the threat picture.

Technical view

hfsc_qlen_notify() was not idempotent. Repeated calls could decrement cl_nactive or remove the same red-black-tree node more than once. The stable fixes guard update_vf() with cl_nactive and use RB_EMPTY_NODE() and RB_CLEAR_NODE() around eltree_remove(). The supplied sources do not describe the resulting corruption mechanism in greater detail.

Likely exposure

Potentially exposed systems run affected Linux kernel versions and permit a low-privileged local actor to reach the HFSC queueing path. The bundle identifies affected version records across several kernel branches through 6.15, but distribution backports may change exposure. Confirm status using the applicable distribution advisory and package changelog.

Exploitation context

The bundle marks this CVE as absent from KEV and provides no cited evidence of active exploitation or a public exploit. Its CVSS 3.1 vector is local, low complexity, low privilege, and requires no user interaction, with high potential impact across confidentiality, integrity, and availability.

Researcher notes

The security-relevant change makes notification handling repeat-safe: update_vf() runs only while cl_nactive is nonzero, and tree removal checks and clears node state. The supplied record does not identify a CWE, explain the precise impact primitive, or establish exploitability beyond the CVSS vector. Version conclusions should account for stable and distribution backports.

Mitigation direction

  • Install the vendor-supported kernel update containing the applicable stable fix.
  • Consult the distribution advisory to map backported fixes to installed package versions.
  • Restrict unnecessary local access and privileges until affected systems are updated.
  • Reboot into the patched kernel after installation.

Validation and detection

  • Inventory running kernel versions on Linux systems.
  • Compare each package version against its distribution security advisory.
  • Verify the applicable stable fix is present in the vendor kernel changelog.
  • Identify systems configured to use the HFSC queueing scheduler.
  • After updating, confirm the patched kernel is actively running.
Prepared
Confidence
medium
Sources
10

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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2025-38177 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
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
2ADP providers
11Source 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-2025-38177Attack 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
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux959466588aa7f84ccf79ae36a1d89542eaf9aaec, 959466588aa7f84ccf79ae36a1d89542eaf9aaec, 959466588aa7f84ccf79ae36a1d89542eaf9aaec, 959466588aa7f84ccf79ae36a1d89542eaf9aaec, 959466588aa7f84ccf79ae36a1d89542eaf9aaec, 959466588aa7f84ccf79ae36a1d89542eaf9aaec, 959466588aa7f84ccf79ae36a1d89542eaf9aaec, 959466588aa7f84ccf79ae36a1d89542eaf9aaecunaffected
LinuxLinux4.14, 0, 5.4.297, 5.10.241, 5.15.190, 6.1.138, 6.6.90, 6.12.28, 6.14.6, 6.15affected
Weakness

CWE details

No CWE listed

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