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Actively exploited · Published Apr 17, 2021 · Assigned by canonical

CVE-2021-3493

High 8.8 Exploited

In plain English

A high-severity security flaw in linux kernel from Ubuntu. Attackers are actively exploiting it in the wild (listed by CISA on October 20, 2022). The chance it is exploited in the next 30 days is estimated at 49.2% (higher than 99% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit, public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.8High
Exploit odds (30 days)49.2%top 1.1% of all CVEs
Exploited in the wildYesCISA KEV since Oct 20, 2022
Attack tooling2Metasploit, Public PoC

CISA guidance

Apply updates per vendor instructions.

Federal agencies must remediate by Nov 10, 2022.

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12linux5.10.38-1DEBIAN-CVE-2021-3493
Debian:13linux5.10.38-1DEBIAN-CVE-2021-3493
Debian:14linux5.10.38-1DEBIAN-CVE-2021-3493
Ubuntu:22.04:LTSlinux-intel-iot-realtimeno fix listedUBUNTU-CVE-2021-3493
Ubuntu:24.04:LTSlinux-raspi-realtimeno fix listedUBUNTU-CVE-2021-3493
Ubuntu:22.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2021-3493

Affected products (as reported)

VendorProductVersions
Ubuntu linux kernel 5.8 kernel – before 5.8.0-50.565.4 kernel – before 5.4.0-72.804.15 kernel – before 4.15.0-142.1464.4 kernel – before 4.4.0-209.241

Weakness: CWE-270 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

References