CVE-2026-63833 (GCVE-0-2026-63833)
Vulnerability from cvelistv5
Published
2026-07-19 12:02
Modified
2026-08-17 04:51
Severity ?
7.1 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Summary
In the Linux kernel, the following vulnerability has been resolved: ntfs3: reject direct userspace writes to reserved $LX* xattrs NTFS3 uses $LXUID, $LXGID, $LXMOD and $LXDEV as internal WSL permission metadata and reloads them into i_uid, i_gid and i_mode from ntfs_get_wsl_perm(). Because the empty-prefix xattr handler also lets file owners call setxattr() on these names directly, an unprivileged writer on a writable ntfs3 mount can plant root ownership and S_ISUID on their own file and gain euid 0 after inode reload. Reject direct userspace writes to the reserved $LX* names. Internal ntfs3 metadata updates are unchanged because ntfs_save_wsl_perm() writes them via ntfs_set_ea() directly. [almaz.alexandrovich@paragon-software.com: added an additional check for non privileged users]
References
Impacted products
Vendor Product Version
Linux Linux Version: be71b5cba2e6485e8959da7a9f9a44461a1bb074
Version: be71b5cba2e6485e8959da7a9f9a44461a1bb074
Version: be71b5cba2e6485e8959da7a9f9a44461a1bb074
Version: be71b5cba2e6485e8959da7a9f9a44461a1bb074
Version: be71b5cba2e6485e8959da7a9f9a44461a1bb074
Version: be71b5cba2e6485e8959da7a9f9a44461a1bb074
Version: be71b5cba2e6485e8959da7a9f9a44461a1bb074
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ntfs3/xattr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ntfs3/xattr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "5.15"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.211",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.177",
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            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.144",
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              "status": "unaffected",
              "version": "6.12.95",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.38",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.211",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.177",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
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                {
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                {
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                  "versionStartIncluding": "5.15",
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nntfs3: reject direct userspace writes to reserved $LX* xattrs\n\nNTFS3 uses $LXUID, $LXGID, $LXMOD and $LXDEV as internal WSL\npermission metadata and reloads them into i_uid, i_gid and i_mode\nfrom ntfs_get_wsl_perm().\n\nBecause the empty-prefix xattr handler also lets file owners call\nsetxattr() on these names directly, an unprivileged writer on a\nwritable ntfs3 mount can plant root ownership and S_ISUID on their own\nfile and gain euid 0 after inode reload.\n\nReject direct userspace writes to the reserved $LX* names. Internal\nntfs3 metadata updates are unchanged because ntfs_save_wsl_perm()\nwrites them via ntfs_set_ea() directly.\n\n[almaz.alexandrovich@paragon-software.com: added an additional check for non privileged users]"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires the setxattr/fsetxattr syscall against an ntfs3-mounted filesystem; ksmbd and nfsd prefix xattr names with \"user.\" so they cannot reach the empty-prefix \"$LX*\" handler.\nAC:L - An attacker reliably sets the three 4-byte xattrs on a file they own, then forces inode reload via dentry eviction under self-induced memory pressure or umount/remount in a user namespace.\nPR:L - Any unprivileged local user with write access to their own file on a writable ntfs3 mount can trigger the bug; mounting ntfs3 in a user namespace only requires CAP_SYS_ADMIN within that namespace, which counts as Low.\nUI:N - No victim interaction is needed at exploit time; the attacker uses their own local account on an already-mounted writable ntfs3 volume (common on dual-boot/shared NTFS data partitions).\nS:U - Successful exploitation yields host root privileges within the same kernel security domain; it is standard local privilege escalation, not a cross-boundary escape.\nC:H - Planting root ownership and S_ISUID on an executable and executing it after inode reload grants effective UID 0, providing full read access to all kernel-managed data on the system.\nI:H - The bug allows arbitrary tampering with kernel-trusted ownership and permission metadata, culminating in root code execution with unrestricted ability to modify any system data.\nA:N - The vulnerability is a metadata permission bypass with no kernel crash, panic, hang, or denial-of-service component; availability is unaffected by the flaw itself."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:51:43.293Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e574af95234afc3c725988bbc1fdeb46b9f386a4"
        },
        {
          "url": "https://git.kernel.org/stable/c/2c3cd6da4a14380ef79e34bd9dff7caf46687477"
        },
        {
          "url": "https://git.kernel.org/stable/c/e8852ae29868e449fdb47eebc28f35fb80741a5f"
        },
        {
          "url": "https://git.kernel.org/stable/c/f8d420949b335a4b51d06ab276beee6b8dfdc909"
        },
        {
          "url": "https://git.kernel.org/stable/c/5e658b9245a52d838ef93729a7bc07de8e19deb7"
        },
        {
          "url": "https://git.kernel.org/stable/c/293a84fa40b3a1b3471c0545722724bc10973f76"
        },
        {
          "url": "https://git.kernel.org/stable/c/5b08dccecf825cbf905f348bc6ccb497507e28e2"
        }
      ],
      "title": "ntfs3: reject direct userspace writes to reserved $LX* xattrs",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63833",
    "datePublished": "2026-07-19T12:02:25.469Z",
    "dateReserved": "2026-07-19T07:54:57.015Z",
    "dateUpdated": "2026-08-17T04:51:43.293Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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