CVE-2021-27851

Local privilege escalation in GNU Guix via guix-daemon and '--keep-failed'

Severity Score

5.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

A security vulnerability that can lead to local privilege escalation has been found in ’guix-daemon’. It affects multi-user setups in which ’guix-daemon’ runs locally. The attack consists in having an unprivileged user spawn a build process, for instance with `guix build`, that makes its build directory world-writable. The user then creates a hardlink to a root-owned file such as /etc/shadow in that build directory. If the user passed the --keep-failed option and the build eventually fails, the daemon changes ownership of the whole build tree, including the hardlink, to the user. At that point, the user has write access to the target file. Versions after and including v0.11.0-3298-g2608e40988, and versions prior to v1.2.0-75109-g94f0312546 are vulnerable.

Se ha encontrado una vulnerabilidad de seguridad en "guix-daemon" que puede conllevar a una escalada de privilegios local. Afecta a las configuraciones multiusuario en las que "guix-daemon" se ejecuta localmente. El ataque consiste en hacer que un usuario no privilegiado genere un proceso de compilación, por ejemplo con "guix build", que hace que su directorio de compilación sea world-writable. Luego, el usuario crea un vínculo físico a un archivo de propiedad root tal y como /etc/shadow en ese directorio de compilación. Si el usuario pasó la opción --keep-failed y finalmente se produce un fallo en la compilación, el demonio cambia la propiedad de todo el árbol de compilación, incluido el enlace físico, al usuario. En ese momento, el usuario tiene acceso de escritura al archivo de destino. Las versiones posteriores a la v0.11.0-3298-g2608e40988 y las versiones anteriores a la v1.2.0-75109-g94f0312546 son vulnerables

*Credits: Nathan Nye of WhiteBeam Security

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

None

Attack Vector

Local

Attack Complexity

Low

Authentication

None

Confidentiality

None

Integrity

Partial

Availability

None

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2021-03-01 CVE Reserved
2021-04-26 CVE Published
2023-03-08 EPSS Updated
2024-09-17 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-59: Improper Link Resolution Before File Access ('Link Following')
CWE-264: Permissions, Privileges, and Access Controls

CAPEC

References (2)

URL	Tag	Source

URL	Date	SRC

URL	Date	SRC
https://bugs.gnu.org/47229	2022-07-29
https://guix.gnu.org/en/blog/2021/risk-of-local-privilege-escalation-via-guix-daemon	2022-07-29

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Gnu Search vendor "Gnu"		Guix Search vendor "Gnu" for product "Guix"				>= 0.11.0 < 1.2.0 Search vendor "Gnu" for product "Guix" and version " >= 0.11.0 < 1.2.0"		-		Affected