CVE-2021-3493

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.

• CWE-270
• CWE-863

• http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.htmlExploit, Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.htmlPress/Media Coverage, Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.htmlExploit, Third Party Advisory, VDB Entry
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52Mailing List, Patch, Third Party Advisory
• https://ubuntu.com/security/notices/USN-4917-1Vendor Advisory
• https://www.openwall.com/lists/oss-security/2021/04/16/1Mailing List, Third Party Advisory
• http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.htmlExploit, Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.htmlPress/Media Coverage, Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.htmlExploit, Third Party Advisory, VDB Entry
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52Mailing List, Patch, Third Party Advisory
• https://ubuntu.com/security/notices/USN-4917-1Vendor Advisory
• https://www.openwall.com/lists/oss-security/2021/04/16/1Mailing List, Third Party Advisory
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3493US Government Resource

Published

Apr 17, 2021

Last Modified

Jun 17, 2026

Status

Analyzed

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