{"id":"CVE-2026-63896","summary":"usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: composite: fix integer underflow in WebUSB GET_URL handling\n\nThe WebUSB GET_URL handler in composite_setup() narrows\nlanding_page_length to fit the host-supplied wLength using\n\n\tlanding_page_length = w_length\n\t\t- WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset;\n\nIf wLength is smaller than WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH the\nunsigned subtraction wraps, and the subsequent\n\n\tmemcpy(url_descriptor-\u003eURL,\n\t       cdev-\u003elanding_page + landing_page_offset,\n\t       landing_page_length - landing_page_offset);\n\nends up copying close to UINT_MAX bytes from cdev-\u003elanding_page into\ncdev-\u003ereq-\u003ebuf.  KASAN reports a slab-out-of-bounds in composite_setup\non the kmalloc-2k gadget_info allocation, and FORTIFY_SOURCE traps the\nmemcpy as a 4294967293-byte field-spanning write into\nurl_descriptor-\u003eURL (size 252).\n\nA USB host can reach this from a single SETUP packet against any\ngadget that has webusb/use=1 and a landingPage configured.\n\nHandle the small-wLength case before the math: when the host requested\nfewer bytes than the URL descriptor header, only the header is\nmeaningful and no URL bytes need to be copied.  Setting\nlanding_page_length to landing_page_offset makes the existing memcpy a\nno-op and leaves the descriptor returned to the host unchanged for all\nlarger wLength values.","modified":"2026-07-21T03:46:41.577528086Z","published":"2026-07-19T14:55:06.152Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63896.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/046870ff6b6f7b743c953c061043a9b30700d491"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6c5dbc104dadd79fc2923497c20bae759a18758c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a20f0ccf45708af6e063c7234c215d364b00de25"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f5869dfaa89854dcf34121036294d42d6c7acb8f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f8f5a8f48c7cae3fac85e04b593bd47939f9725f"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63896.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63896"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"93c473948c588978cd55d9a3adad8b3e8057aa21"},{"fixed":"046870ff6b6f7b743c953c061043a9b30700d491"},{"fixed":"f5869dfaa89854dcf34121036294d42d6c7acb8f"},{"fixed":"f8f5a8f48c7cae3fac85e04b593bd47939f9725f"},{"fixed":"a20f0ccf45708af6e063c7234c215d364b00de25"},{"fixed":"6c5dbc104dadd79fc2923497c20bae759a18758c"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-63896.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.3.0"},{"fixed":"6.6.143"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.93"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.35"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.12"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-63896.json"}}],"schema_version":"1.7.5"}