Vulnerability-Lookup

CVE-2026-64294 (GCVE-0-2026-64294)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:49 – Updated: 2026-07-25 08:49

Title

mm: do file ownership checks with the proper mount idmap

Summary

In the Linux kernel, the following vulnerability has been resolved: mm: do file ownership checks with the proper mount idmap Ever since idmapped mounts were introduced, inode ownership checks (for side-channel protection) in mincore() and madvise(MADV_PAGEOUT) were done against the nop_mnt_idmap, which completely ignores the file's mount's idmap. This results in odd edgecases like: 1) mount/bind-mount with an idmap userA:userB:1 2) userB runs an owner_or_capable() check on file that is owned by userA on-disk/in-memory, but owned by userB after idmap translation 3) owner_or_capable() mysteriously fails as the correct idmap wasn't supplied In the case of mincore/madvise MADV_PAGEOUT, this is usually benign, because file_permission(file, MAY_WRITE) will probably succeed, as it uses the proper idmap internally, but it does not need to be the case on e.g a 0444 file where even the owner itself doesn't have permissions to write to it. Since this is clearly not trivial to get right, introduce a file_owner_or_capable() that can carry the correct semantics, and switch the various users in mm to it. The issue was found by manual code inspection & an off-list discussion with Jan Kara.

Severity

No CVSS data available.

Assigner

Linux

References

5 references

URL	Tags
https://git.kernel.org/stable/c/744b23aa430d52f5c…
https://git.kernel.org/stable/c/8344bdf0629457e53…
https://git.kernel.org/stable/c/5c942ad7df75925ee…
https://git.kernel.org/stable/c/04ba248d02d9eaa3d…
https://git.kernel.org/stable/c/e187bc02f8fa4226d…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 9caccd41541a6f7d6279928d9f971f6642c361af , < 744b23aa430d52f5c8e4dbff7d71496d6643bed2 (git) Affected: 9caccd41541a6f7d6279928d9f971f6642c361af , < 8344bdf0629457e532797b42d9d2bbf2a2900bbf (git) Affected: 9caccd41541a6f7d6279928d9f971f6642c361af , < 5c942ad7df75925ee166e7f0fb36892d8dde376b (git) Affected: 9caccd41541a6f7d6279928d9f971f6642c361af , < 04ba248d02d9eaa3d9077b00a6134caa75fa3e90 (git) Affected: 9caccd41541a6f7d6279928d9f971f6642c361af , < e187bc02f8fa4226d62814592cf064ee4557c470 (git)
Linux	Linux	Affected: 5.12 Unaffected: 0 , < 5.12 (semver) Unaffected: 6.6.145 , ≤ 6.6.* (semver) Unaffected: 6.12.96 , ≤ 6.12.* (semver) Unaffected: 6.18.39 , ≤ 6.18.* (semver) Unaffected: 7.1.4 , ≤ 7.1.* (semver) Unaffected: 7.2-rc3 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
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              "versionType": "semver"
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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        },
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          "url": "https://git.kernel.org/stable/c/e187bc02f8fa4226d62814592cf064ee4557c470"
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    "datePublished": "2026-07-25T08:49:32.570Z",
    "dateReserved": "2026-07-19T15:36:31.778Z",
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      "date": "2026-07-27",
      "epss": "0.002",
      "percentile": "0.10098"
    },
    "microsoft_vex": {
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      "cve": "CVE-2026-64294",
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      "initial_release_date": "2026-07-26T01:01:33.000Z",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "mm: do file ownership checks with the proper mount idmap",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64294.json",
      "version": "1"
    },
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    "suse_vex": {
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      "cve": "CVE-2026-64294",
      "id": "CVE-2026-64294",
      "initial_release_date": "2026-07-25T16:46:23Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64294",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64294.json",
      "version": "2"
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}

GHSA-RGG7-9234-2H22

Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-07-25 12:31

Details

In the Linux kernel, the following vulnerability has been resolved:

mm: do file ownership checks with the proper mount idmap

Ever since idmapped mounts were introduced, inode ownership checks (for side-channel protection) in mincore() and madvise(MADV_PAGEOUT) were done against the nop_mnt_idmap, which completely ignores the file's mount's idmap. This results in odd edgecases like:

1) mount/bind-mount with an idmap userA:userB:1 2) userB runs an owner_or_capable() check on file that is owned by userA on-disk/in-memory, but owned by userB after idmap translation 3) owner_or_capable() mysteriously fails as the correct idmap wasn't supplied

In the case of mincore/madvise MADV_PAGEOUT, this is usually benign, because file_permission(file, MAY_WRITE) will probably succeed, as it uses the proper idmap internally, but it does not need to be the case on e.g a 0444 file where even the owner itself doesn't have permissions to write to it.

Since this is clearly not trivial to get right, introduce a file_owner_or_capable() that can carry the correct semantics, and switch the various users in mm to it.

The issue was found by manual code inspection & an off-list discussion with Jan Kara.

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-64294"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-25T10:17:10Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: do file ownership checks with the proper mount idmap\n\nEver since idmapped mounts were introduced, inode ownership checks (for\nside-channel protection) in mincore() and madvise(MADV_PAGEOUT) were done\nagainst the nop_mnt_idmap, which completely ignores the file\u0027s mount\u0027s\nidmap.  This results in odd edgecases like:\n\n1) mount/bind-mount with an idmap userA:userB:1\n2) userB runs an owner_or_capable() check on file that is owned by userA\non-disk/in-memory, but owned by userB after idmap translation\n3) owner_or_capable() mysteriously fails as the correct idmap wasn\u0027t supplied\n\nIn the case of mincore/madvise MADV_PAGEOUT, this is usually benign,\nbecause file_permission(file, MAY_WRITE) will probably succeed, as it uses\nthe proper idmap internally, but it does not need to be the case on e.g a\n0444 file where even the owner itself doesn\u0027t have permissions to write to\nit.\n\nSince this is clearly not trivial to get right, introduce a\nfile_owner_or_capable() that can carry the correct semantics, and switch\nthe various users in mm to it.\n\nThe issue was found by manual code inspection \u0026 an off-list discussion\nwith Jan Kara.",
  "id": "GHSA-rgg7-9234-2h22",
  "modified": "2026-07-25T12:31:29Z",
  "published": "2026-07-25T12:31:29Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64294"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/04ba248d02d9eaa3d9077b00a6134caa75fa3e90"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5c942ad7df75925ee166e7f0fb36892d8dde376b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/744b23aa430d52f5c8e4dbff7d71496d6643bed2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8344bdf0629457e532797b42d9d2bbf2a2900bbf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e187bc02f8fa4226d62814592cf064ee4557c470"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-64294 (GCVE-0-2026-64294)

GHSA-RGG7-9234-2H22

Tags

Sightings

Nomenclature