{"id":"CVE-2021-3493","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-3493","generatedAt":"2026-10-31T15:00:14.738Z","title":"Linux Kernel Privilege Escalation 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.","published":"2021-04-17T05:15:15.000Z","lastModified":"2026-06-17T04:05:12.000Z","status":"Analyzed","sourceIdentifier":"security@ubuntu.com","cvss":{"version":"3.1","score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-270","CWE-863"],"affected":["canonical/ubuntu linux"],"epss":{"score":0.49166,"percentile":0.98882,"date":"2026-10-30","history":[]},"kev":{"listed":true,"dateAdded":"2022-10-20","dueDate":"2022-11-10","knownRansomwareCampaignUse":"Unknown","notes":"Apply updates per vendor instructions.\nhttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52; https://nvd.nist.gov/vuln/detail/CVE-2021-3493"},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"Known to be exploited in the wild (CISA KEV, CISA remediation deadline 10 November 2022). Treat as an emergency change: patch or isolate now, then hunt for prior compromise."},"changes":[],"references":[{"url":"http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html","tags":["Exploit","Third Party Advisory","VDB Entry"],"source":"security@ubuntu.com"},{"url":"http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html","tags":["Press/Media Coverage","Third Party Advisory","VDB Entry"],"source":"security@ubuntu.com"},{"url":"http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html","tags":["Exploit","Third Party Advisory","VDB Entry"],"source":"security@ubuntu.com"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52","tags":["Mailing List","Patch","Third Party Advisory"],"source":"security@ubuntu.com"},{"url":"https://ubuntu.com/security/notices/USN-4917-1","tags":["Vendor Advisory"],"source":"security@ubuntu.com"},{"url":"https://www.openwall.com/lists/oss-security/2021/04/16/1","tags":["Mailing List","Third Party Advisory"],"source":"security@ubuntu.com"},{"url":"http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html","tags":["Exploit","Third Party Advisory","VDB Entry"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html","tags":["Press/Media Coverage","Third Party Advisory","VDB Entry"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html","tags":["Exploit","Third Party Advisory","VDB Entry"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52","tags":["Mailing List","Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://ubuntu.com/security/notices/USN-4917-1","tags":["Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.openwall.com/lists/oss-security/2021/04/16/1","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3493","tags":["US Government Resource"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-3493","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}