{"id":"CVE-2026-63833","state":"PUBLISHED","title":"ntfs3: reject direct userspace writes to reserved $LX* xattrs","description":"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]","publishedAt":"2026-07-19T12:02:25.469Z","updatedAt":"2026-10-19T20:07:49.624Z","severity":{"score":7.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"e574af95234afc3c725988bbc1fdeb46b9f386a4","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"2c3cd6da4a14380ef79e34bd9dff7caf46687477","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"e8852ae29868e449fdb47eebc28f35fb80741a5f","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"f8d420949b335a4b51d06ab276beee6b8dfdc909","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"5e658b9245a52d838ef93729a7bc07de8e19deb7","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"293a84fa40b3a1b3471c0545722724bc10973f76","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"5b08dccecf825cbf905f348bc6ccb497507e28e2","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ntfs3/xattr.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"5.15.211","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.177","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.144","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.95","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.38","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.3","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ntfs3/xattr.c"]}],"references":["https://git.kernel.org/stable/c/e574af95234afc3c725988bbc1fdeb46b9f386a4","https://git.kernel.org/stable/c/2c3cd6da4a14380ef79e34bd9dff7caf46687477","https://git.kernel.org/stable/c/e8852ae29868e449fdb47eebc28f35fb80741a5f","https://git.kernel.org/stable/c/f8d420949b335a4b51d06ab276beee6b8dfdc909","https://git.kernel.org/stable/c/5e658b9245a52d838ef93729a7bc07de8e19deb7","https://git.kernel.org/stable/c/293a84fa40b3a1b3471c0545722724bc10973f76","https://git.kernel.org/stable/c/5b08dccecf825cbf905f348bc6ccb497507e28e2"],"weaknesses":["CWE-862"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63833.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63833","state":"PUBLISHED","datePublished":"2026-07-19T12:02:25.469Z","dateUpdated":"2026-10-19T20:07:49.624Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.015Z"},"containers":{"cna":{"title":"ntfs3: reject direct userspace writes to reserved $LX* xattrs","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]"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"e574af95234afc3c725988bbc1fdeb46b9f386a4","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"2c3cd6da4a14380ef79e34bd9dff7caf46687477","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"e8852ae29868e449fdb47eebc28f35fb80741a5f","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"f8d420949b335a4b51d06ab276beee6b8dfdc909","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"5e658b9245a52d838ef93729a7bc07de8e19deb7","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"293a84fa40b3a1b3471c0545722724bc10973f76","versionType":"git"},{"version":"be71b5cba2e6485e8959da7a9f9a44461a1bb074","status":"affected","lessThan":"5b08dccecf825cbf905f348bc6ccb497507e28e2","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ntfs3/xattr.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"5.15.211","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.177","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.144","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.95","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.38","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.3","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ntfs3/xattr.c"]}],"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"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N","baseScore":7.1,"baseSeverity":"HIGH"},"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":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T04:51:43.293Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"5.15.211"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.177"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.144"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.12.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.18.38"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.1.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-63833","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:31:27.797089Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","lang":"en","type":"CWE","description":"CWE-862 Missing Authorization"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:07:49.624Z"}}]}}}