310 lines
17 KiB
JSON
310 lines
17 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-63808",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-07-19T07:54:57.013Z",
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"datePublished": "2026-07-19T12:02:11.323Z",
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"dateUpdated": "2026-10-19T20:07:48.432Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-08-17T04:51:14.402Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nexfat: fix potential use-after-free in exfat_find_dir_entry()\n\nIn exfat_find_dir_entry(), the buffer_head obtained from\nexfat_get_dentry() is released with brelse(bh) before the fall-through\nTYPE_EXTEND branch reads the directory entry through ep (which points\ninto bh->b_data):\n\n\tbrelse(bh);\n\tif (entry_type == TYPE_EXTEND) {\n\t\t...\n\t\tlen = exfat_extract_uni_name(ep, entry_uniname);\n\t\t...\n\t}\n\nAfter brelse() drops our reference, nothing guarantees that the\nunderlying page backing bh->b_data remains valid for the subsequent\nexfat_extract_uni_name() read. This is the same pattern fixed in\ncommit fc961522ddbd (\"exfat: Fix potential use after free in\nexfat_load_upcase_table()\").\n\nMove brelse(bh) so it runs after ep is no longer dereferenced on\neach branch.\n\nConfirmed on QEMU x86_64 with CONFIG_KASAN=y + CONFIG_DEBUG_PAGEALLOC=y\n+ CONFIG_PAGE_POISONING=y on linux-next, using a crafted exFAT image\n(long filename with same-hash collisions forcing the TYPE_EXTEND path).\nWith a debug-only invalidate_bdev() inserted between brelse(bh) and\nthe ep read to make the stale-deref window deterministic, the\nunpatched kernel faults:\n\n BUG: KASAN: use-after-free in exfat_find_dir_entry+0x133b/0x15a0\n BUG: unable to handle page fault for address: ffff88801a5fa0c2\n Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\n RIP: 0010:exfat_find_dir_entry+0x1188/0x15a0\n\nWith this patch applied, the same instrumented harness completes\ncleanly under the same sanitizer stack. I have not reproduced a\ncrash on an uninstrumented kernel under ordinary reclaim; the\ninstrumented A/B establishes the lifetime violation and that the\npatch closes it, not an unaided triggerability claim."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 9.8,
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"baseSeverity": "CRITICAL"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:N - exfat_find_dir_entry() is invoked during VFS directory lookups on mounted exFAT volumes, reachable remotely when that volume is exported via ksmbd or nfsd (common on NAS/router USB shares). A network client resolving paths on the share triggers server-side exfat_lookup without local shell access.\nAC:L - The attacker fully controls the crafted exFAT image to force the TYPE_EXTEND code path and can repeatedly trigger lookups (including concurrent SMB/NFS requests and memory pressure) to win the post-brelse buffer reclaim window. UAF lifetime violations are treated as low complexity per kernel guidance.\nPR:N - Exploitation requires only access to the mounted exFAT filesystem, not real root; guest/anonymous SMB shares on consumer NAS devices and auto-mounted removable media grant unprivileged attackers filesystem access without elevated kernel credentials.\nUI:N - Once a crafted exFAT image is present on a shared or auto-mounted volume, triggering the bug requires only automated path lookups (SMB OPEN/LOOKUP, openat, statx) with no additional victim interaction beyond normal filesystem access.\nS:U - Successful exploitation compromises kernel memory within the same security authority; this is a standard kernel memory corruption issue, not a cross-boundary escape such as VM guest-to-host breakout.\nC:H - The UAF reads freed buffer_head page cache memory through exfat_extract_uni_name(), enabling out-of-bounds kernel heap reads and information disclosure from attacker-influenced reclaimed data.\nI:H - Use-after-free on buffer_head data provides a foundation for heap grooming and arbitrary memory corruption primitives that can be leveraged for kernel code execution and integrity compromise.\nA:H - The bug is a confirmed kernel use-after-free that produced a KASAN fault and page fault oops; even without full exploitation it can cause kernel crashes and denial of service."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"fs/exfat/dir.c"
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],
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"versions": [
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{
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"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
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"lessThan": "e6f1a11cfb808441a43ffae9b476cc135732cd27",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
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"lessThan": "e48f413c2815787b8cade2795e194e3c4cd782ef",
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"status": "affected",
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},
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{
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"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
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"lessThan": "06c4e1e9967d332ac33ba38b7819851089ff9359",
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"status": "affected",
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{
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"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
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"lessThan": "8e0abc17fbd7e305802e84fe98b4950d50f9c433",
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"status": "affected",
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},
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{
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"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
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"lessThan": "4d101016d5e587f820b3ae2d5bb6770d86342649",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
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"lessThan": "adfacfbaeae2cb760f492357cc36b41f84ef7f86",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
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"lessThan": "708b97e792945d3e4653939fd3405d71a61ad065",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
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"lessThan": "3f5f8ee9917cc2b9076ac533492d8a200edcabb8",
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"status": "affected",
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"versionType": "git"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"fs/exfat/dir.c"
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],
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"versions": [
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{
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"version": "5.7",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "5.7",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "5.10.260",
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"lessThanOrEqual": "5.10.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "5.15.211",
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"lessThanOrEqual": "5.15.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.1.177",
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"lessThanOrEqual": "6.1.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.6.144",
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"lessThanOrEqual": "6.6.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.12.95",
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"lessThanOrEqual": "6.12.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.18.38",
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"lessThanOrEqual": "6.18.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.1.3",
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"lessThanOrEqual": "7.1.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.2",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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{
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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "5.7",
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/e6f1a11cfb808441a43ffae9b476cc135732cd27"
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},
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{
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"url": "https://git.kernel.org/stable/c/e48f413c2815787b8cade2795e194e3c4cd782ef"
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},
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{
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"url": "https://git.kernel.org/stable/c/06c4e1e9967d332ac33ba38b7819851089ff9359"
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},
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{
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"url": "https://git.kernel.org/stable/c/8e0abc17fbd7e305802e84fe98b4950d50f9c433"
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},
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{
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"url": "https://git.kernel.org/stable/c/4d101016d5e587f820b3ae2d5bb6770d86342649"
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},
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{
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"url": "https://git.kernel.org/stable/c/adfacfbaeae2cb760f492357cc36b41f84ef7f86"
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},
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{
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"url": "https://git.kernel.org/stable/c/708b97e792945d3e4653939fd3405d71a61ad065"
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},
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{
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"url": "https://git.kernel.org/stable/c/3f5f8ee9917cc2b9076ac533492d8a200edcabb8"
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}
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],
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"title": "exfat: fix potential use-after-free in exfat_find_dir_entry()",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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},
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"adp": [
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{
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"metrics": [
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{
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"other": {
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"type": "ssvc",
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"content": {
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"id": "CVE-2026-63808",
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"role": "CISA Coordinator",
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"options": [
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{
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"Exploitation": "none"
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},
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{
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"Automatable": "yes"
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},
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{
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"Technical Impact": "total"
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}
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],
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"version": "2.0.3",
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"timestamp": "2026-10-16T15:30:56.233960Z"
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}
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}
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}
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],
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"problemTypes": [
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{
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"descriptions": [
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{
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"lang": "en",
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"type": "CWE",
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"cweId": "CWE-416",
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"description": "CWE-416 Use After Free"
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}
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]
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}
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],
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"title": "CISA ADP Vulnrichment",
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"providerMetadata": {
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"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"shortName": "CISA-ADP",
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"dateUpdated": "2026-10-19T20:07:48.432Z"
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}
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}
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]
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}
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} |