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CVE-2021-3493

🔥 Known Exploited (CISA KEV)HIGH

8.8

CVSS Severity Score

EPSS Score66.1960%

EPSS Percentile89.88th

Published2021-04-17

Last Modified2025-10-28

Data SourcesNVDCISA KEVFIRST.org EPSS

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.

Affected Platforms (CPE)

💻

Canonical

Ubuntu Linux

< 18.04>= 18.04.1 and < 20.04< 20.10

References & Advisories

🔗 http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html

🔗 http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html

🔗 http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html

🔗 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52

🔗 https://ubuntu.com/security/notices/USN-4917-1

🔗 https://www.openwall.com/lists/oss-security/2021/04/16/1

🔗 http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html

🔗 http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html

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