CVE-2026-31538Network attack vector

Unauthenticated service interruption via receive-credit race

Published Apr 24, 2026 · Updated Apr 24, 2026

A receive-credit race in the Linux Kernel SMB Direct server in 6.18 through 6.18.10 and 6.19 allows remote attackers to interrupt service. In fs/smb/server/transport_rdma.c, manage_credits_prior_sending grants credits from posted receive buffers even when the peer has already consumed a credit. Unauthenticated network access to a KSMBD SMB Direct service over RDMA is required; the vendor does not specify whether interruption produces a hang or crash.

CVSS severity7.5
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A receive-credit race in the Linux Kernel SMB Direct server in 6.18 through 6.18.10 and 6.19 allows remote attackers to interrupt service. In fs/smb/server/transport_rdma.c, manage_credits_prior_sending grants credits from posted receive buffers even when the peer has already consumed a credit. Unauthenticated network access to a KSMBD SMB Direct service over RDMA is required; the vendor does not specify whether interruption produces a hang or crash.

The record

CVE
CVE-2026-31538
Published
Apr 24, 2026
Updated
Apr 24, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.18
  2. Affected versionversion=89b021a72663c4d96d8a8b85272bb42d991a1c6f <26ad87a2cfb8c1384620d1693a166ed87303046e
  3. Affected versionversion=89b021a72663c4d96d8a8b85272bb42d991a1c6f <66c082e3d4651e8629a393a9e182b01eb50fb0a3
  4. Affected versionversion=89b021a72663c4d96d8a8b85272bb42d991a1c6f <809cbd31aa4f87a1b889532244c9cf30eb022385

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.18; version=89b021a72663c4d96d8a8b85272bb42d991a1c6f <26ad87a2cfb8c1384620d1693a166ed87303046e; version=89b021a72663c4d96d8a8b85272bb42d991a1c6f <66c082e3d4651e8629a393a9e182b01eb50fb0a3; version=89b021a72663c4d96d8a8b85272bb42d991a1c6f <809cbd31aa4f87a1b889532244c9cf30eb022385

Published CVSS scores

7.5kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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