CVEvulnerability

CVE-2021-3493

7.8 HIGH Known exploited Published 2021-04-17 Modified 2026-06-17 Official page ↗

CISA Known Exploited Vulnerability

Linux Kernel Privilege Escalation Vulnerability — Linux Kernel

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.

Added to KEV
2022-10-20
Remediation due
2022-11-10
Ransomware use
Unknown
Required action
Apply updates per vendor instructions.
Notes
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52; https://nvd.nist.gov/vuln/detail/CVE-2021-3493
Status
Analyzed
Published
2021-04-17
Last modified
2026-06-17
Assigner
[email protected]
CVSS 3.1 ([email protected])
8.8 HIGH — CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CVSS 3.1 ([email protected])
7.8 HIGH — CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0 ([email protected])
7.2 HIGH — AV:L/AC:L/Au:N/C:C/I:C/A:C
Weaknesses
CWE-270, CWE-863

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 configurations

• canonical ubuntu linux (< 18.04) • canonical ubuntu linux (>= 18.04.1 < 20.04) • canonical ubuntu linux (< 20.10)

Related

Weakness · CWE (2)

  • CWE-270 Privilege Context Switching Error weakness
  • CWE-863 Incorrect Authorization weakness

References