{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-63895", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-63895", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-07-19T14:55:05.479Z", "updatedAt": "2026-07-19T14:55:05.479Z", "importedAt": "2026-10-24T01:58:20.586Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "usb: gadget: f_fs: copy only received bytes on short ep0 read", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: copy only received bytes on short ep0 read\n\nffs_ep0_read() allocates its control-OUT data buffer with\nkmalloc() (not kzalloc) at the Length value from the Setup\npacket, then copies that full len to userspace regardless of\nhow many bytes were actually received:\n\n data = kmalloc(len, GFP_KERNEL);\n ...\n ret = __ffs_ep0_queue_wait(ffs, data, len);\n if ((ret > 0) && (copy_to_user(buf, data, len)))\n ret = -EFAULT;\n\n__ffs_ep0_queue_wait() returns req->actual, which on a short\ncontrol OUT transfer is strictly less than len. The\ncopy_to_user() call still copies len bytes, so on a short OUT\nthe last (len - ret) bytes of the kmalloc() buffer --\nuninitialised slab residue -- are delivered to the FunctionFS\ndaemon.\n\nShort ep0 OUT completions are specified USB control-transfer\nbehavior and are produced by in-tree UDCs:\n\n * dwc2 continues on req->actual < req->length for ep0 DATA OUT\n (short-not-ok is the only ep0-OUT stall path).\n * aspeed_udc ends ep0 OUT on rx_len < ep->ep.maxpacket.\n * renesas_usbf logs \"ep0 short packet\" and completes the\n request.\n * dwc3 stalls on short IN but not on short OUT.\n\nA short ep0 OUT is therefore not evidence of a broken UDC; it is\na normal condition f_fs has to cope with. The sibling gadgetfs\nimplementation in drivers/usb/gadget/legacy/inode.c already does\nthis correctly via min(len, dev->req->actual) before\ncopy_to_user(). This patch brings f_fs.c to the same safe\npattern rather than trimming at a defensive layer.\n\nThe bug is reached from the FunctionFS device node, which in\nreal deployments is owned by the privileged gadget daemon\n(adbd, UMS, composite gadget services, etc.); it is not\nreachable from unprivileged userspace. Linux host stacks\nnormally reject short-wLength control OUTs before they reach\nthe gadget, so reproducing this required a build that\nbypasses that host-side check. With the bypass in place, a\n1-byte payload on a 64-byte Setup produces 63 bytes of\nnon-canary slab residue in the daemon's read buffer.\n\nFix by copying only ret (actually received) bytes to\nuserspace.", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "status": "affected", "versionType": "git", "lessThan": "90ccf5fb63243fae1b4b3200f3310500500ecf2e" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "status": "affected", "versionType": "git", "lessThan": "af32dbb2ca0b3d09271ab718d13857a457fa16f2" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "status": "affected", "versionType": "git", "lessThan": "e835bf9a055f71874065a40780ca5560b7df8b33" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "status": "affected", "versionType": "git", "lessThan": "88874a19b2b093bfaaa1c0090fa536c44da8c08b" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "status": "affected", "versionType": "git", "lessThan": "607730a414773a7cbe3037a64a6c64e72689ff5e" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "status": "affected", "versionType": "git", "lessThan": "23c1f7deb9dd8447ecde749850676302aa1e2bd3" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "status": "affected", "versionType": "git", "lessThan": "4e036c10e7f4df5d951c69cc3697bc8e209c6d02" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "2.6.35", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "2.6.35" }, { "version": "5.15.210", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.176", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.143", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.93", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.35", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.0.12", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.0.*" }, { "version": "7.1", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }