CVE-2026-63896: Linux kernel · usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 12 Nov 2026, 15:35 UTC
Rated High by Threat Radar's AI analysis · No CVSS score from NVD or the CNA
Thin evidence
One scorer or noneExploitation evidence
Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 12 Nov 2026.
What to do
AI-suggested
A fix for this vulnerability has been implemented in the Linux kernel by properly handling the case when the host-supplied wLength is smaller than the URL descriptor header length, preventing the integer underflow and out-of-bounds memory copy. Users and administrators should apply the official Linux kernel updates that include this fix. Since this is a kernel-level vulnerability, updating to a patched kernel version is the recommended remediation.
Description
A vulnerability in the Linux kernel's USB gadget composite driver related to the WebUSB GET_URL handler could cause an integer underflow. This flaw allows an unsigned subtraction to wrap when the host-supplied wLength is smaller than the URL descriptor header length, leading to an out-of-bounds memory copy. The issue is triggered by a USB host sending a crafted SETUP packet to any gadget with webusb/use=1 and a landingPage configured. The flaw has been fixed by properly handling cases where wLength is smaller than the header length to prevent excessive copying.
References
- git.kernel.org/stable/c/046870ff6b6f7b743c953c061043a9b30700d491 (opens in a new tab)
- git.kernel.org/stable/c/f5869dfaa89854dcf34121036294d42d6c7acb8f (opens in a new tab)
- git.kernel.org/stable/c/f8f5a8f48c7cae3fac85e04b593bd47939f9725f (opens in a new tab)
- git.kernel.org/stable/c/a20f0ccf45708af6e063c7234c215d364b00de25 (opens in a new tab)
- git.kernel.org/stable/c/6c5dbc104dadd79fc2923497c20bae759a18758c (opens in a new tab)