CVE-2026-63896

Crash via WebUSB descriptor length underflow

Published Jul 19, 2026 · Updated Jul 19, 2026

Integer underflow in the Linux Kernel USB gadget subsystem allows physically proximate attackers to crash configured WebUSB gadgets. composite_setup() subtracts the descriptor-header size from an undersized host-controlled wLength, wraps the unsigned length, and passes the resulting near-UINT_MAX size to memcpy(). A single USB SETUP packet reaches the out-of-bounds copy only when webusb/use is enabled and a landingPage is configured, resulting in a kernel memory-safety trap or crash.

CVSS severityUnavailable
Unscored
EPSS probability0.21%
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 the Linux Kernel USB gadget subsystem allows physically proximate attackers to crash configured WebUSB gadgets. composite_setup() subtracts the descriptor-header size from an undersized host-controlled wLength, wraps the unsigned length, and passes the resulting near-UINT_MAX size to memcpy(). A single USB SETUP packet reaches the out-of-bounds copy only when webusb/use is enabled and a landingPage is configured, resulting in a kernel memory-safety trap or crash.

The record

CVE
CVE-2026-63896
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499.004
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 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=6.3
  2. Affected versionversion=93c473948c588978cd55d9a3adad8b3e8057aa21 <046870ff6b6f7b743c953c061043a9b30700d491
  3. Affected versionversion=93c473948c588978cd55d9a3adad8b3e8057aa21 <6c5dbc104dadd79fc2923497c20bae759a18758c
  4. Affected versionversion=93c473948c588978cd55d9a3adad8b3e8057aa21 <a20f0ccf45708af6e063c7234c215d364b00de25
  5. Affected versionversion=93c473948c588978cd55d9a3adad8b3e8057aa21 <f5869dfaa89854dcf34121036294d42d6c7acb8f
  6. Affected versionversion=93c473948c588978cd55d9a3adad8b3e8057aa21 <f8f5a8f48c7cae3fac85e04b593bd47939f9725f

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.3; version=93c473948c588978cd55d9a3adad8b3e8057aa21 <046870ff6b6f7b743c953c061043a9b30700d491; version=93c473948c588978cd55d9a3adad8b3e8057aa21 <6c5dbc104dadd79fc2923497c20bae759a18758c; version=93c473948c588978cd55d9a3adad8b3e8057aa21 <a20f0ccf45708af6e063c7234c215d364b00de25; version=93c473948c588978cd55d9a3adad8b3e8057aa21 <f5869dfaa89854dcf34121036294d42d6c7acb8f; version=93c473948c588978cd55d9a3adad8b3e8057aa21 <f8f5a8f48c7cae3fac85e04b593bd47939f9725f

Published CVSS scores

No CVSS assessment is available in this record.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

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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