CVE-2021-3493
Linux Kernel Privilege Escalation Vulnerability
Does this matter?
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.
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 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 49.17% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 20 October 2022 · due 10 November 2022
- Weakness
- CWE-270, CWE-863
- Affected
- canonical/ubuntu linux
- Source
- security@ubuntu.com
EPSS 49.2% since 30 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
CISA notes
Apply updates per vendor instructions. https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52; https://nvd.nist.gov/vuln/detail/CVE-2021-3493
References
- 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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.