168 lines
11 KiB
JSON
168 lines
11 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-2026-64031",
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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": "2026-07-19T07:54:57.028Z",
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"datePublished": "2026-07-19T15:39:21.609Z",
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"dateUpdated": "2026-09-14T11:58:35.405Z"
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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": "2026-09-14T11:58:35.405Z"
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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\nerofs: fix managed cache race for unaligned extents\n\nAfter unaligned compressed extents were introduced, the following race\ncould occur:\n\n[Thread 1] [Thread 2]\n(z_erofs_fill_bio_vec)\n<handle a Z_EROFS_PREALLOCATED_FOLIO folio>\n...\nfilemap_add_folio (1)\n (z_erofs_bind_cache)\n <the same folio is found..>\n ..\n ..\nfolio_attach_private (2)\n filemap_add_folio (3) again\n\nSince (1) is executed but (2) hasn't been executed yet, it's possible\nthat another thread finds the same managed folio in z_erofs_bind_cache()\nfor a different pcluster and calls filemap_add_folio() again since\nfolio->private is still Z_EROFS_PREALLOCATED_FOLIO.\n\nFix this by explicitly clearing folio->private before making the folio\nvisible in the managed cache so that another pcluster can simply wait\non the locked managed folio as what we did for other shared cases [1].\n\nThis only impacts unaligned data compression (`-E48bit` with zstd,\nfor example).\n\n[1] Commit 9e2f9d34dd12 (\"erofs: handle overlapped pclusters out of\n crafted images properly\") was originally introduced to handle crafted\n overlapped extents, but it addresses unaligned extents as well."
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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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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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:L - The bug is reached only through local VFS read paths (`read`/`pread`/`mmap` faults) on a mounted EROFS volume, flowing through `z_erofs_read_folio`/`z_erofs_readahead` → `z_erofs_runqueue` → `z_erofs_submit_queue` → `z_erofs_fill_bio_vec` and `z_erofs_bind_cache`. There is no network-facing handler; exploitation requires local filesystem access.\nAC:L - The race is between concurrent read/decompress threads that the attacker fully controls by issuing parallel reads against a crafted image with overlapping unaligned compressed extents. No timing or layout conditions outside attacker control are required beyond crafting the image and spawning concurrent I/O.\nPR:L - Triggering the vulnerable managed-cache path requires mounting a crafted EROFS image with unaligned zstd extents, which is achievable with CAP_SYS_ADMIN inside an unprivileged user namespace (`unshare -Urn`) plus loop mount. After mount, only normal unprivileged file read access is needed to hit the race.\nUI:N - Once the attacker can mount the crafted image (e.g., via user namespace), exploitation is fully automated through concurrent reads and requires no additional victim interaction such as opening a specific application or clicking a link.\nS:U - Impact is confined to kernel memory corruption and privilege escalation within the same kernel/host security boundary; this is not a VM escape, IOMMU bypass, or cross-authority sandbox breakout.\nC:H - The race leaves managed folios visible in the page cache while `folio->private` still marks them preallocated, allowing duplicate `filemap_add_folio` and conflicting `folio_attach_private`/`folio_detach_private` bindings to different pclusters—classic page-cache corruption that can yield arbitrary kernel memory disclosure via confused folio ownership.\nI:H - Associating one managed folio with multiple pclusters corrupts `folio->private` and compressed-bvec references, creating use-after-free/refcount confusion in the managed cache that is exploitable for arbitrary kernel writes or control-flow hijack, not merely a benign error return.\nA:H - The corrupted managed-cache state can cause kernel oops/panic, hung tasks, or deadlock (similar overlapped-pcluster crafted-image failures previously caused syzbot hangs), and any successful UAF in this path also implies high availability impact even before full exploitation."
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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/erofs/zdata.c"
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],
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"versions": [
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{
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"version": "722f0fcdb0bb7d12a5c6d9460b9a7de1f735f36d",
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"lessThan": "2718cdb6db0fdbe375e61f2980aada27bafb323e",
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"status": "affected",
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"versionType": "git"
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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/erofs/zdata.c"
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],
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"versions": [
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{
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"version": "6.15",
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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": "6.15",
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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": "6.18.34",
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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": "7.0.11",
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"lessThanOrEqual": "7.0.*",
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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",
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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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"references": [
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{
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"url": "https://git.kernel.org/stable/c/2718cdb6db0fdbe375e61f2980aada27bafb323e"
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},
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{
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"url": "https://git.kernel.org/stable/c/425d32d6288d7d845e486af9419bbedccd8c9103"
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},
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{
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"url": "https://git.kernel.org/stable/c/038166f873c4caf6e85cfd4ea0c5a5ba297b4e8b"
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},
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{
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"url": "https://git.kernel.org/stable/c/649932fc3815eda2f24eb4de4b3a5e94886ee0b9"
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}
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],
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"title": "erofs: fix managed cache race for unaligned extents",
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