CVE-2021-3493

2021-04-1704:20:16

CWE-270

canonical

www.cve.org

linux kernel

overlayfs

elevated privileges

user namespaces

file capabilities

ubuntu kernel

unprivileged mounts

CVSS3

8.8

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

AI Score

8.2

Confidence

High

EPSS

0.008

Percentile

82.3%

JSON

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.

CNA Affected

[
  {
    "product": "linux kernel",
    "vendor": "Ubuntu",
    "versions": [
      {
        "lessThan": "5.8.0-50.56",
        "status": "affected",
        "version": "5.8 kernel",
        "versionType": "custom"
      },
      {
        "lessThan": "5.4.0-72.80",
        "status": "affected",
        "version": "5.4 kernel",
        "versionType": "custom"
      },
      {
        "lessThan": "4.15.0-142.146",
        "status": "affected",
        "version": "4.15 kernel",
        "versionType": "custom"
      },
      {
        "lessThan": "4.4.0-209.241",
        "status": "affected",
        "version": "4.4 kernel",
        "versionType": "custom"
      }
    ]
  }
]