VulnerabilityPublished 19 Jul 2026

CVE-2026-63896: Linux kernel · usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling

Source GCVE Database

Not known to be exploited.

Data as of 26 Oct 2026, 14:05 UTC

Severity

Medium

Rated by Threat Radar · No CVSS score from NVD or the CNA

EPSS: 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-5hvq-fg66-prgg

What to do

AI-suggested

The vulnerability description indicates that a fix has been implemented in the Linux kernel source code by handling the small wLength case before performing arithmetic to prevent integer underflow. Users should monitor official Linux kernel advisories and apply updates when available. In the meantime, disabling or avoiding use of USB gadgets with webusb/use=1 and landingPage configured may reduce exposure.

Description

A vulnerability in the Linux kernel's USB gadget composite driver related to WebUSB GET_URL handling causes an integer underflow. This underflow can lead to an out-of-bounds memory copy when the host supplies a small wLength value, potentially causing memory corruption. The issue arises because the code subtracts a constant from wLength without checking if wLength is smaller than that constant, resulting in an unsigned wraparound. The vulnerability is triggered by a USB host sending a crafted SETUP packet to a gadget with webusb/use=1 and a landingPage configured. The fix involves handling the small wLength case before the arithmetic to prevent the underflow and avoid copying excessive bytes.

Impact

This vulnerability allows a USB host to cause an out-of-bounds memory copy in the kernel's USB gadget driver, potentially leading to memory corruption. Such corruption could result in system instability, crashes, or other undefined behavior. There is no evidence of known exploits in the wild. The impact is limited to systems running vulnerable Linux kernel versions with USB gadgets configured with webusb/use=1 and a landingPage.

References

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