CVE-2026-31617

Kernel service interruption via NTB length underflow

Published Apr 24, 2026 · Updated Apr 24, 2026

Integer underflow in Linux Kernel USB NCM gadget handling allows physically proximate attackers to interrupt the affected kernel. ncm_unwrap_ntb() accepts a host-supplied block_len below opts->ndp_size, so unsigned subtraction defeats NDP and datagram bounds checks and lets skb_put_data() read past the transfer. Exploitation requires a malicious USB host connected to an enabled CDC-NCM gadget; published scoring limits confirmed impact to availability.

CVSS severity5.5
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer underflow in Linux Kernel USB NCM gadget handling allows physically proximate attackers to interrupt the affected kernel. ncm_unwrap_ntb() accepts a host-supplied block_len below opts->ndp_size, so unsigned subtraction defeats NDP and datagram bounds checks and lets skb_put_data() read past the transfer. Exploitation requires a malicious USB host connected to an enabled CDC-NCM gadget; published scoring limits confirmed impact to availability.

The record

CVE
CVE-2026-31617
Published
Apr 24, 2026
Updated
Apr 24, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-191, T1200
Attack vector
physical
Privileges
Unavailable

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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6762f8a95772265dd0c2ffe7f400493f3115b135
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <74908b0318d1df1188457040b8714ff4d4b68126
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8757a2593631443648218244b9788e193ae0fdc1
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d58ba8f6546232f8414f396c189297dbee03f1a7

What conditions does exploitation require?

Attack vectorphysical
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6762f8a95772265dd0c2ffe7f400493f3115b135; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <74908b0318d1df1188457040b8714ff4d4b68126; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8757a2593631443648218244b9788e193ae0fdc1; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d58ba8f6546232f8414f396c189297dbee03f1a7

Published CVSS scores

5.5redhat-SADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/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)
Vectorphysical
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-191Integer Underflow (Wrap or Wraparound)
T1200Hardware Additions

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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