CVE-2026-63833: Linux kernel · ntfs3: reject direct userspace writes to reserved $LX* xattrs
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.1 High · fixed in 5.15.0-1117.124~20.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 13:47 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +43
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available and should be applied to affected Linux kernel versions. The fix rejects direct userspace writes to the reserved $LX* extended attribute names, preventing privilege escalation via this vector. Users should update their Linux kernel to a fixed version as per the vendor advisory. No additional mitigation is required beyond applying the official fix.
Description
A vulnerability in the Linux kernel's ntfs3 driver allowed unprivileged users on writable ntfs3 mounts to write directly to reserved extended attributes ($LX*), enabling them to escalate privileges to effective root (euid 0). This occurs because ntfs3 uses these attributes for internal WSL permission metadata, and direct user writes to these reserved names were not properly rejected. The issue has been fixed by rejecting direct userspace writes to these reserved $LX* xattrs.
References
- nvd.nist.gov/vuln/detail/CVE-2026-63833 (opens in a new tab)
- git.kernel.org/stable/c/293a84fa40b3a1b3471c0545722724bc10973f76 (opens in a new tab)
- git.kernel.org/stable/c/2c3cd6da4a14380ef79e34bd9dff7caf46687477 (opens in a new tab)
- git.kernel.org/stable/c/5b08dccecf825cbf905f348bc6ccb497507e28e2 (opens in a new tab)
- git.kernel.org/stable/c/5e658b9245a52d838ef93729a7bc07de8e19deb7 (opens in a new tab)
- git.kernel.org/stable/c/e574af95234afc3c725988bbc1fdeb46b9f386a4 (opens in a new tab)
- git.kernel.org/stable/c/e8852ae29868e449fdb47eebc28f35fb80741a5f (opens in a new tab)
- git.kernel.org/stable/c/f8d420949b335a4b51d06ab276beee6b8dfdc909 (opens in a new tab)
- ubuntu.com/security/CVE-2026-63833 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-63833 (opens in a new tab)
- git.kernel.org/linus/5b08dccecf825cbf905f348bc6ccb497507e28e2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8727-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8760-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8800-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8760-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8878-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8877-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8886-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-2 (opens in a new tab)