{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63895", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.019Z", "datePublished": "2026-07-19T14:55:05.479Z", "dateUpdated": "2026-07-19T14:55:05.479Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-07-19T14:55:05.479Z" }, "descriptions": [ { "lang": "en", "value": "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": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/usb/gadget/function/f_fs.c" ], "versions": [ { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "lessThan": "90ccf5fb63243fae1b4b3200f3310500500ecf2e", "status": "affected", "versionType": "git" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "lessThan": "af32dbb2ca0b3d09271ab718d13857a457fa16f2", "status": "affected", "versionType": "git" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "lessThan": "e835bf9a055f71874065a40780ca5560b7df8b33", "status": "affected", "versionType": "git" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "lessThan": "88874a19b2b093bfaaa1c0090fa536c44da8c08b", "status": "affected", "versionType": "git" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "lessThan": "607730a414773a7cbe3037a64a6c64e72689ff5e", "status": "affected", "versionType": "git" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "lessThan": "23c1f7deb9dd8447ecde749850676302aa1e2bd3", "status": "affected", "versionType": "git" }, { "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0", "lessThan": "4e036c10e7f4df5d951c69cc3697bc8e209c6d02", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/usb/gadget/function/f_fs.c" ], "versions": [ { "version": "2.6.35", "status": "affected" }, { "version": "0", "lessThan": "2.6.35", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.210", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.176", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.143", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.93", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.35", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.12", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "5.15.210" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "6.1.176" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "6.6.143" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "6.12.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "6.18.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "7.0.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.35", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/90ccf5fb63243fae1b4b3200f3310500500ecf2e" }, { "url": "https://git.kernel.org/stable/c/af32dbb2ca0b3d09271ab718d13857a457fa16f2" }, { "url": "https://git.kernel.org/stable/c/e835bf9a055f71874065a40780ca5560b7df8b33" }, { "url": "https://git.kernel.org/stable/c/88874a19b2b093bfaaa1c0090fa536c44da8c08b" }, { "url": "https://git.kernel.org/stable/c/607730a414773a7cbe3037a64a6c64e72689ff5e" }, { "url": "https://git.kernel.org/stable/c/23c1f7deb9dd8447ecde749850676302aa1e2bd3" }, { "url": "https://git.kernel.org/stable/c/4e036c10e7f4df5d951c69cc3697bc8e209c6d02" } ], "title": "usb: gadget: f_fs: copy only received bytes on short ep0 read", "x_generator": { "engine": "bippy-1.2.0" } } } }