Vulnerability Details 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.731
EPSS Ranking 98.7%
CVSS Severity
CVSS v3 Score 8.8
CVSS v2 Score 7.2
Proposed Action
The overlayfs stacking file system in Linux kernel does not properly validate the application of file capabilities against user namespaces, which could lead to privilege escalation.
Ransomware Campaign
Unknown
References
- 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
- 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
Products affected by CVE-2021-3493
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cpe:2.3:o:canonical:ubuntu_linux:10.04
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cpe:2.3:o:canonical:ubuntu_linux:10.04.1
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cpe:2.3:o:canonical:ubuntu_linux:10.04.2
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cpe:2.3:o:canonical:ubuntu_linux:10.04.3
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cpe:2.3:o:canonical:ubuntu_linux:10.04.4
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cpe:2.3:o:canonical:ubuntu_linux:12.04
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cpe:2.3:o:canonical:ubuntu_linux:12.04.1
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cpe:2.3:o:canonical:ubuntu_linux:12.04.2
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cpe:2.3:o:canonical:ubuntu_linux:12.04.3
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cpe:2.3:o:canonical:ubuntu_linux:12.04.4
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cpe:2.3:o:canonical:ubuntu_linux:12.04.5
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cpe:2.3:o:canonical:ubuntu_linux:14.04
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cpe:2.3:o:canonical:ubuntu_linux:14.04.1
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cpe:2.3:o:canonical:ubuntu_linux:14.04.2
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cpe:2.3:o:canonical:ubuntu_linux:14.04.3
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cpe:2.3:o:canonical:ubuntu_linux:14.04.4
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cpe:2.3:o:canonical:ubuntu_linux:14.04.5
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cpe:2.3:o:canonical:ubuntu_linux:14.04.6
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cpe:2.3:o:canonical:ubuntu_linux:16.04
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cpe:2.3:o:canonical:ubuntu_linux:16.04.1
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cpe:2.3:o:canonical:ubuntu_linux:16.04.2
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cpe:2.3:o:canonical:ubuntu_linux:16.04.3
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cpe:2.3:o:canonical:ubuntu_linux:16.04.4
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cpe:2.3:o:canonical:ubuntu_linux:16.04.5
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cpe:2.3:o:canonical:ubuntu_linux:16.04.6
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cpe:2.3:o:canonical:ubuntu_linux:17.10
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cpe:2.3:o:canonical:ubuntu_linux:18.04.1
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cpe:2.3:o:canonical:ubuntu_linux:18.04.2
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cpe:2.3:o:canonical:ubuntu_linux:18.04.3
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cpe:2.3:o:canonical:ubuntu_linux:18.04.4
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cpe:2.3:o:canonical:ubuntu_linux:18.04.5
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cpe:2.3:o:canonical:ubuntu_linux:18.04.6
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cpe:2.3:o:canonical:ubuntu_linux:19.04
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cpe:2.3:o:canonical:ubuntu_linux:20.04
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cpe:2.3:o:canonical:ubuntu_linux:6.06
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cpe:2.3:o:canonical:ubuntu_linux:6.06.1
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cpe:2.3:o:canonical:ubuntu_linux:6.06.2
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cpe:2.3:o:canonical:ubuntu_linux:8.04
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cpe:2.3:o:canonical:ubuntu_linux:8.04.1
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cpe:2.3:o:canonical:ubuntu_linux:8.04.2
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cpe:2.3:o:canonical:ubuntu_linux:8.04.3
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cpe:2.3:o:canonical:ubuntu_linux:8.04.4