CVE-2021-3493

Linux Kernel Privilege Escalation Vulnerability

Severity Score

7.8

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

Yes

*KEV

Decision

*SSVC

Descriptions

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.

La implementación de overlayfs en el kernel de Linux no comprobó apropiadamente con respecto a los espacios de nombre de los usuarios, la configuración de las capacidades de los archivos en un sistema de archivos subyacente. Debido a la combinación de los espacios de nombre de usuarios no privilegiados junto con un parche incluido en el kernel de Ubuntu para permitir montajes de superposición no privilegiados, un atacante podría usar esto para alcanzar privilegios elevados

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.

*Credits: An independent security researcher reporting to the SSD Secure Disclosure program

CVSS Scores

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Attack Vector

Local

Attack Complexity

Low

Authentication

None

Confidentiality

Complete

Integrity

Complete

Availability

Complete

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2021-04-12 CVE Reserved
2021-04-12 First Exploit
2021-04-16 CVE Published
2022-10-20 Exploited in Wild
2022-11-10 KEV Due Date
2024-02-09 EPSS Updated
2024-09-17 CVE Updated

CWE

CWE-270: Privilege Context Switching Error
CWE-863: Incorrect Authorization

CAPEC

References (18)

URL	Tag	Source
http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html	Third Party Advisory
https://www.openwall.com/lists/oss-security/2021/04/16/1	Mailing List

URL	Date	SRC
https://github.com/briskets/CVE-2021-3493	2021-09-28
https://github.com/inspiringz/CVE-2021-3493	2021-07-07
https://github.com/oneoy/CVE-2021-3493	2021-04-20
https://github.com/cerodah/overlayFS-CVE-2021-3493	2021-09-12
https://github.com/derek-turing/CVE-2021-3493	2021-07-16
https://github.com/puckiestyle/CVE-2021-3493	2021-09-28
https://github.com/smallkill/CVE-2021-3493	2023-05-21
https://github.com/Abdennour-py/CVE-2021-3493	2021-04-20
https://github.com/fei9747/CVE-2021-3493	2021-09-28
https://github.com/ptkhai15/OverlayFS---CVE-2021-3493	2023-08-25
https://github.com/pmihsan/OverlayFS-CVE-2021-3493	2023-01-16
http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html	2024-09-17
http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html	2024-09-17
https://raw.githubusercontent.com/rapid7/metasploit-framework/master/modules/exploits/linux/local/cve_2021_3493_overlayfs.rb	2021-04-12

URL	Date	SRC
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52	2023-07-07

URL	Date	SRC
https://ubuntu.com/security/notices/USN-4917-1	2023-07-07

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Canonical Search vendor "Canonical"		Ubuntu Linux Search vendor "Canonical" for product "Ubuntu Linux"				< 18.04 Search vendor "Canonical" for product "Ubuntu Linux" and version " < 18.04"		lts		Affected
Canonical Search vendor "Canonical"		Ubuntu Linux Search vendor "Canonical" for product "Ubuntu Linux"				>= 18.04.1 < 20.04 Search vendor "Canonical" for product "Ubuntu Linux" and version " >= 18.04.1 < 20.04"		lts		Affected
Canonical Search vendor "Canonical"		Ubuntu Linux Search vendor "Canonical" for product "Ubuntu Linux"				< 20.10 Search vendor "Canonical" for product "Ubuntu Linux" and version " < 20.10"		-		Affected