usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63896
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:07 UTC
Updated2026-07-19 16:17:07 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling The WebUSB GET_URL handler in composite_setup() narrows landing_page_length to fit the host-supplied wLength using landing_page_length = w_length - WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset; If wLength is smaller than WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH the unsigned subtraction wraps, and the subsequent memcpy(url_descriptor->URL, cdev->landing_page + landing_page_offset, landing_page_length - landing_page_offset); ends up copying close to UINT_MAX bytes from cdev->landing_page into cdev->req->buf. KASAN reports a slab-out-of-bounds in composite_setup on the kmalloc-2k gadget_info allocation, and FORTIFY_SOURCE traps the memcpy as a 4294967293-byte field-spanning write into url_descriptor->URL (size 252). A USB host can reach this from a single SETUP packet against any gadget that has webusb/use=1 and a landingPage configured. Handle the small-wLength case before the math: when the host requested fewer bytes than the URL descriptor header, only the header is meaningful and no URL bytes need to be copied. Setting landing_page_length to landing_page_offset makes the existing memcpy a no-op and leaves the descriptor returned to the host unchanged for all larger wLength values.

Risk And Classification

EPSS: 0.002000000 probability, percentile 0.100180000 (date 2026-07-20)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 93c473948c588978cd55d9a3adad8b3e8057aa21 046870ff6b6f7b743c953c061043a9b30700d491 git Not specified
CNA Linux Linux affected 93c473948c588978cd55d9a3adad8b3e8057aa21 f5869dfaa89854dcf34121036294d42d6c7acb8f git Not specified
CNA Linux Linux affected 93c473948c588978cd55d9a3adad8b3e8057aa21 f8f5a8f48c7cae3fac85e04b593bd47939f9725f git Not specified
CNA Linux Linux affected 93c473948c588978cd55d9a3adad8b3e8057aa21 a20f0ccf45708af6e063c7234c215d364b00de25 git Not specified
CNA Linux Linux affected 93c473948c588978cd55d9a3adad8b3e8057aa21 6c5dbc104dadd79fc2923497c20bae759a18758c git Not specified
CNA Linux Linux affected 6.3 Not specified
CNA Linux Linux unaffected 6.3 semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/f5869dfaa89854dcf34121036294d42d6c7acb8f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6c5dbc104dadd79fc2923497c20bae759a18758c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f8f5a8f48c7cae3fac85e04b593bd47939f9725f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a20f0ccf45708af6e063c7234c215d364b00de25 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/046870ff6b6f7b743c953c061043a9b30700d491 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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