#VU71486 Race condition in Samba - CVE-2021-20251

Vulnerability identifier: #VU71486

Vulnerability risk: Low

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

CVE-ID: CVE-2021-20251

CWE-ID: CWE-362

Exploitation vector: Adjecent network

Exploit availability: No public exploit available

Vulnerable software:
Samba

Software vendor:
Samba

The vulnerability allows a remote attacker to perform a brute-force attack.

The vulnerability exists due to a race condition in Samba when incrementing bad password attempts. Each connection to Samba gets a separate process, and each process loads, increments, and saves the bad password count without any coordination. A remote attacker can perform a brute-force attack using multiple threats and bypass imposed limits on the number of allowed incorrect passwords.

Install updates from vendor's website.

• https://bugzilla.samba.org/show_bug.cgi?id=14611
• https://gitlab.com/samba-team/samba/-/merge_requests/2708