CVE-2026-64031 (GCVE-0-2026-64031)

Vulnerability from cvelistv5 – Published: 2026-07-19 15:39 – Updated: 2026-08-05 12:38
VLAI
Title
erofs: fix managed cache race for unaligned extents
Summary
In the Linux kernel, the following vulnerability has been resolved: erofs: fix managed cache race for unaligned extents After unaligned compressed extents were introduced, the following race could occur: [Thread 1] [Thread 2] (z_erofs_fill_bio_vec) <handle a Z_EROFS_PREALLOCATED_FOLIO folio> ... filemap_add_folio (1) (z_erofs_bind_cache) <the same folio is found..> .. .. folio_attach_private (2) filemap_add_folio (3) again Since (1) is executed but (2) hasn't been executed yet, it's possible that another thread finds the same managed folio in z_erofs_bind_cache() for a different pcluster and calls filemap_add_folio() again since folio->private is still Z_EROFS_PREALLOCATED_FOLIO. Fix this by explicitly clearing folio->private before making the folio visible in the managed cache so that another pcluster can simply wait on the locked managed folio as what we did for other shared cases [1]. This only impacts unaligned data compression (`-E48bit` with zstd, for example). [1] Commit 9e2f9d34dd12 ("erofs: handle overlapped pclusters out of crafted images properly") was originally introduced to handle crafted overlapped extents, but it addresses unaligned extents as well.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 7361d1e3763baaf7b9349c576137851458ad38d1 , < 425d32d6288d7d845e486af9419bbedccd8c9103 (git)
Affected: 7361d1e3763baaf7b9349c576137851458ad38d1 , < 038166f873c4caf6e85cfd4ea0c5a5ba297b4e8b (git)
Affected: 7361d1e3763baaf7b9349c576137851458ad38d1 , < 649932fc3815eda2f24eb4de4b3a5e94886ee0b9 (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.34 , ≤ 6.18.* (semver)
Unaffected: 7.0.11 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/erofs/zdata.c"
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          "vendor": "Linux",
          "versions": [
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        {
          "lang": "en",
          "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\u003chandle a Z_EROFS_PREALLOCATED_FOLIO folio\u003e\n...\nfilemap_add_folio (1)\n                                             (z_erofs_bind_cache)\n                                             \u003cthe same folio is found..\u003e\n                                             ..\n                                             ..\nfolio_attach_private (2)\n                                             filemap_add_folio (3) again\n\nSince (1) is executed but (2) hasn\u0027t been executed yet, it\u0027s 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-\u003eprivate is still Z_EROFS_PREALLOCATED_FOLIO.\n\nFix this by explicitly clearing folio-\u003eprivate 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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
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              "lang": "en",
              "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` \u2192 `z_erofs_runqueue` \u2192 `z_erofs_submit_queue` \u2192 `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-\u003eprivate` still marks them preallocated, allowing duplicate `filemap_add_folio` and conflicting `folio_attach_private`/`folio_detach_private` bindings to different pclusters\u2014classic 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-\u003eprivate` 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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      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:38:25.282Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/425d32d6288d7d845e486af9419bbedccd8c9103"
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          "url": "https://git.kernel.org/stable/c/038166f873c4caf6e85cfd4ea0c5a5ba297b4e8b"
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        {
          "url": "https://git.kernel.org/stable/c/649932fc3815eda2f24eb4de4b3a5e94886ee0b9"
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      "title": "erofs: fix managed cache race for unaligned extents",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64031",
    "datePublished": "2026-07-19T15:39:21.609Z",
    "dateReserved": "2026-07-19T07:54:57.028Z",
    "dateUpdated": "2026-08-05T12:38:25.282Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-08-05T14:21:24+00:00",
      "cve": "CVE-2026-64031",
      "id": "CVE-2026-64031",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: erofs: fix managed cache race for unaligned extents",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64031.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-07-30T16:33:26Z",
      "cve": "CVE-2026-64031",
      "id": "CVE-2026-64031",
      "initial_release_date": "2026-07-21T13:01:09Z",
      "product_status:known_not_affected": "296",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64031",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64031.json",
      "version": "3"
    }
  }
}



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