Security restrictions bypass in Samba

1) Link following

EUVDB-ID: #VU59345

Risk: Low

CVSSv3.1: 2.3 [CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-43566

CWE-ID: CWE-59 - Improper Link Resolution Before File Access ('Link Following')

Exploit availability: No

Description

The vulnerability allows a remote user to bypass implemented security restrictions.

The vulnerability exists due to a symlink race condition when creating directories. A remote authenticated user can use SMB1 or NFS symlink race to create directories on the Unix filesystem outside of the share definition.

Successful exploitation of the vulnerability requites that the user has permissions to create folder in the target directory.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Samba: 4.13.0 - 4.13.15

External links

http://www.samba.org/samba/security/CVE-2021-43566.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the local network (LAN).

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

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