CVE-2019-15793

Mishandling of file-system uid/gid with namespaces in shiftfs

Severity Score

8.8

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

In shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, several locations which shift ids translate user/group ids before performing operations in the lower filesystem were translating them into init_user_ns, whereas they should have been translated into the s_user_ns for the lower filesystem. This resulted in using ids other than the intended ones in the lower fs, which likely did not map into the shifts s_user_ns. A local attacker could use this to possibly bypass discretionary access control permissions.

En shiftfs, un parche no upstream para el Kernel de Linux incluido en las series kernel de Ubuntu versiones 5.0 y 5.3, varias ubicaciones que desplazan los ids traducen los ids de usuario/grupo antes de realizar operaciones en el sistema de archivos inferior los estaban traduciendo a init_user_ns, mientras que deberían haber sido traducidos a s_user_ns para el sistema de archivos inferior. Esto dio lugar a que se utilizaran ids distintos de los previstos en los fs inferiores, que probablemente no se mapearon en los shifts s_user_ns. Un atacante local podría usar esto para posiblemente eludir los permisos de control de acceso discrecional.

Ubuntu suffers from refcount underflow and type confusion vulnerabilities in shiftfs.

*Credits: Jann Horn of Google Project Zero

CVSS Scores

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

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

None

Availability

None

Attack Vector

Local

Attack Complexity

Low

Authentication

None

Confidentiality

Partial

Integrity

Partial

Availability

Partial

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2019-08-29 CVE Reserved
2019-11-13 CVE Published
2019-11-20 First Exploit
2023-03-08 EPSS Updated
2024-09-16 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date

CWE

CWE-276: Incorrect Default Permissions
CWE-538: Insertion of Sensitive Information into Externally-Accessible File or Directory

CAPEC

References (4)

URL	Tag	Source
https://usn.ubuntu.com/usn/usn-4183-1	Third Party Advisory
https://usn.ubuntu.com/usn/usn-4184-1	Third Party Advisory

URL	Date	SRC
https://www.exploit-db.com/exploits/47693	2019-11-20

URL	Date	SRC
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=3644b9d5688da86f18e017c9c580b75cf52927bb	2020-05-01

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				5.0 Search vendor "Linux" for product "Linux Kernel" and version "5.0"		-		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				5.3 Search vendor "Linux" for product "Linux Kernel" and version "5.3"		-		Affected
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"				19.04 Search vendor "Canonical" for product "Ubuntu Linux" and version "19.04"		-		Affected