CVE-2022-38023
samba: RC4/HMAC-MD5 NetLogon Secure Channel is weak and should be avoided
Severity
ImportantRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · December 16, 2022
Updated · February 26, 2026
Description
A flaw was found in samba. The Netlogon RPC implementations may use the rc4-hmac encryption algorithm, which is considered weak and should be avoided even if the client supports more modern encryption types. This issue could allow an attacker who knows the plain text content communicated between the samba client and server to craft data with the same MD5 calculation and replace it without being detected.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
Users can disable MD5-based NetLogon by adding the following snippet to their smb.conf
reject md5 clients = yes
in case there's still need to allow SMB to authenticate to MD5-based NetLogon servers, it's possible to explicitly enable it per-server based:
server reject md5 schannel:<SERVERNAME>$ = no
CVSS / CWE
CVSS 3.1 · 8.1CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE-328 · Use of Weak Hash