CVE-2021-3493
Linux Kernel Privilege Escalation Vulnerability
- High 8.8
- Exploited: added to CISA KEV 20 Oct 2022
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.
Key facts
- Published
- 17 Apr 2021
- Last changed
- 21 Oct 2025
- Assigned by
- canonical
- KEV added
- 20 Oct 2022
- KEV fix due
- 10 Nov 2022
- EPSS
- 49.166% likely to be exploited in the next 30 days, higher than 98.904% of CVEs (scores for 15 Nov 2026)
- SSVC (CISA)
- Exploitation: active; Automatable: no; Technical impact: total
Severity scores
Each score is shown as its source gave it. They are not averaged or merged.
- 8.8CVSS 3.1, Highfrom the CNA (canonical)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
What to do
- Apply https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52CNA solution statement
- Disable unprivileged user namespaces.CNA workaround statement
- Apply updates per vendor instructions.CISA KEV required action
Historical context and remediation
This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.
No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.
Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.
Affected products
| Vendor | Product | Versions |
|---|---|---|
| Ubuntu | linux kernel |
|
Timeline
- 17 Apr 2021 Published
- 20 Oct 2022 CVE-2021-3493 added to CISA KEV
- 20 Oct 2022 Added to the CISA KEV catalogue