Vulnerability Description
The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Canonical | Ubuntu Linux | < 18.04 |
Related Weaknesses (CWE)
References
- http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSExploitThird Party AdvisoryVDB Entry
- http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-EscPress/Media CoverageThird Party AdvisoryVDB Entry
- http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-EscExploitThird Party AdvisoryVDB Entry
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7cMailing ListPatchThird Party Advisory
- https://ubuntu.com/security/notices/USN-4917-1Vendor Advisory
- https://www.openwall.com/lists/oss-security/2021/04/16/1Mailing ListThird Party Advisory
- http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSExploitThird Party AdvisoryVDB Entry
- http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-EscPress/Media CoverageThird Party AdvisoryVDB Entry
- http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-EscExploitThird Party AdvisoryVDB Entry
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7cMailing ListPatchThird Party Advisory
- https://ubuntu.com/security/notices/USN-4917-1Vendor Advisory
- https://www.openwall.com/lists/oss-security/2021/04/16/1Mailing ListThird Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-US Government Resource
FAQ
What is CVE-2021-3493?
CVE-2021-3493 is a vulnerability with a CVSS score of 8.8 (HIGH). The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combinatio...
How severe is CVE-2021-3493?
CVE-2021-3493 has been rated HIGH with a CVSS base score of 8.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-3493?
Check the references section above for vendor advisories and patch information. Affected products include: Canonical Ubuntu Linux.