CVE-2026-31623

Host interruption via USB fragment-array overflow

Published Apr 24, 2026 · Updated Apr 24, 2026

Buffer overflow in the Linux Kernel cdc-phonet driver allows physically proximate attackers to interrupt a host through a malicious USB modem. The rx_complete() path appends full-page bulk transfers to skb_shared_info->frags[] without enforcing the fragment limit. Physical attachment of a device identifying as a CDC Phonet modem is required; the published material does not specify whether the overflow causes a crash, hang, or another availability failure.

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

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Buffer overflow in the Linux Kernel cdc-phonet driver allows physically proximate attackers to interrupt a host through a malicious USB modem. The rx_complete() path appends full-page bulk transfers to skb_shared_info->frags[] without enforcing the fragment limit. Physical attachment of a device identifying as a CDC Phonet modem is required; the published material does not specify whether the overflow causes a crash, hang, or another availability failure.

The record

CVE
CVE-2026-31623
Published
Apr 24, 2026
Updated
Apr 24, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-120, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9989938d13cc5ba8447eeed5a61acfcf61bc6801
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a23b1b1aaf41e174181d5853a70e65d4d01e648c
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c183d5775129a0a7495bd61a6e57ec230dcf01e5
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ebf75c6301c4972a87542ebf2d994c6391eb5d46

What conditions does exploitation require?

Attack vectorphysical
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9989938d13cc5ba8447eeed5a61acfcf61bc6801; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a23b1b1aaf41e174181d5853a70e65d4d01e648c; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c183d5775129a0a7495bd61a6e57ec230dcf01e5; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ebf75c6301c4972a87542ebf2d994c6391eb5d46

Published CVSS scores

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo