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CVE Record

CVE-2025-38115: net_sched: sch_sfq: fix a potential crash on gso_skb handling

In the Linux kernel, the following vulnerability has been resolved: net_sched: sch_sfq: fix a potential crash on gso_skb handling SFQ has an assumption of always being able to queue at least one packet. However, after the blamed commit, sch->q.len can be inflated by packets in sch->gso_skb, and an enqueue() on an empty SFQ qdisc can be followed by an immediate drop. Fix sfq_drop() to properly clear q->tail in this situation. ip netns add lb ip link add dev to-lb type veth peer name in-lb netns lb ethtool -K to-lb tso off # force qdisc to requeue gso_skb ip netns exec lb ethtool -K in-lb gro on # enable NAPI ip link set dev to-lb up ip -netns lb link set dev in-lb up ip addr add dev to-lb 192.168.20.1/24 ip -netns lb addr add dev in-lb 192.168.20.2/24 tc qdisc replace dev to-lb root sfq limit 100 ip netns exec lb netserver netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 &

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 the Linux SFQ network scheduler can crash the kernel when it mishandles queued segmented packets. Exploitation requires local access under the supplied CVSS assessment, so this is not described as an unauthenticated internet attack. Affected multi-user, container, or network-processing systems deserve prompt review.

Executive priority

Treat as a high-priority kernel maintenance issue, especially for shared Linux infrastructure. It is less urgent than a remotely exploitable flaw, but a local user-triggered kernel crash could disrupt critical workloads. Patch through normal emergency maintenance after confirming vendor applicability.

Technical view

SFQ assumes it can always queue at least one packet. Packets held in sch->gso_skb can inflate sch->q.len, allowing enqueue on an empty SFQ queue to trigger an immediate drop. sfq_drop() may then retain an invalid q->tail state, potentially causing a kernel crash. Stable kernel commits clear the tail correctly.

Likely exposure

Exposure is most likely on affected Linux kernels where the SFQ qdisc and GSO requeue behavior are used. The supplied affected-version data is ambiguous and includes commit identifiers alongside release numbers, so administrators should map running distribution kernels to vendor advisories or the referenced stable fixes.

Exploitation context

The supplied CVSS 3.1 score is 7.8 with local access, low complexity, low privileges, and no user interaction. The source bundle provides a crash reproducer but no evidence of malicious exploitation. CISA KEV status is false, and remote exploitation is not established.

Researcher notes

The documented failure concerns inconsistent SFQ queue state when sch->gso_skb inflates the scheduler length and an immediate drop occurs on an otherwise empty queue. The fix clears q->tail in sfq_drop(). Sources establish crash potential, not code execution or observed attacks; avoid inferring broader impact solely from the CVSS confidentiality and integrity metrics.

Mitigation direction

  • Install a vendor-supported kernel update containing the referenced SFQ fix.
  • Check distribution advisories because packaged kernel versions may not match upstream numbering.
  • If updates are delayed, assess whether SFQ usage can be safely avoided under vendor guidance.
  • Prioritize shared, container-hosting, and network-intensive systems where local users may influence traffic scheduling.

Validation and detection

  • Inventory running kernel builds and compare them with distribution security advisories.
  • Confirm whether affected interfaces use the SFQ queueing discipline.
  • Verify the installed kernel incorporates the applicable referenced stable commit.
  • After updating, confirm systems boot normally and report the expected patched kernel build.
  • Review kernel logs for unexplained scheduler faults or crashes; this alone does not prove exploitation.
Prepared
Confidence
medium
Sources
6

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-2025-38115 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-2025-38115Attack 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
LinuxLinuxa53851e2c3218aa30b77abd6e68cf1c371f15afe, a53851e2c3218aa30b77abd6e68cf1c371f15afe, a53851e2c3218aa30b77abd6e68cf1c371f15afe, a53851e2c3218aa30b77abd6e68cf1c371f15afe, a53851e2c3218aa30b77abd6e68cf1c371f15afe, a53851e2c3218aa30b77abd6e68cf1c371f15afe, a53851e2c3218aa30b77abd6e68cf1c371f15afe, a53851e2c3218aa30b77abd6e68cf1c371f15afeunaffected
LinuxLinux4.16, 0, 5.4.295, 5.10.239, 5.15.186, 6.1.142, 6.6.94, 6.12.34, 6.15.3, 6.16affected
Weakness

CWE details

No CWE listed

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