#VU50016 UNIX Hard Link in FreeRADIUS

Vulnerability identifier: #VU50016

Vulnerability risk: Low

CVSSv4.0: 4.4 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: N/A

CWE-ID: CWE-62

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
FreeRADIUS
Server applications / Directory software, identity management

Vendor: FreeRADIUS Server Project

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists in the way FreeRadius is being started on the system. The systemd service file for freeradius runs "chown -R" on a directory before it starts:

  ExecStartPre=-/bin/chown -R radius.radius /run/radiusd

That can be exploited by the "radius" user to gain root privileges. After the service has been started once, the radius user can place a hard link to a root-owned file in /run/radiusd. If the service is later restarted, then the "chown -R" command will give away ownership of that root-owned file to the "radius" user.

As a result, a local user can execute arbitrary code on the system as root.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

FreeRADIUS: 3.0.0.beta0 - 3.0.19

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External links
https://security.gentoo.org/glsa/202101-27
https://bugs.gentoo.org/630910
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=48cd44905411daf0c9914d0df63b387e29e75b10
https://github.com/FreeRADIUS/freeradius-server/commit/26e412b0f775d7219364fec3c204ba6e5877ff1a
https://github.com/FreeRADIUS/freeradius-server/commit/b6f8a6fdd456ebfa889b8867317632bd0ac6b887
https://github.com/FreeRADIUS/freeradius-server/commit/aec8b3e9bbdb67b04fbd3eca8e757e1f114ec613

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.