CVE-2023-3347: Samba: smb2 packet signing is not enforced when "server signing = required" is set

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-07-20 · updated 2026-06-17
Weakness: CWE-347

Description

A vulnerability was found in Samba's SMB2 packet signing mechanism. The SMB2 packet signing is not enforced if an admin configured "server signing = required" or for SMB2 connections to Domain Controllers where SMB2 packet signing is mandatory. This flaw allows an attacker to perform attacks, such as a man-in-the-middle attack, by intercepting the network traffic and modifying the SMB2 messages between client and server, affecting the integrity of the data.

Affected products

Fedoraproject Fedora: 38
Red Hat Enterprise Linux: 8.0, 9.0
RedHat Storage: 3.0
Samba: from 4.17.0 before 4.17.10; from 4.18.0 before 4.18.5 — fixed in 4.17.10, 4.18.5

How to fix

Upgrade to a fixed version: Samba 4.17.10, 4.18.5. Check the vendor advisory for mitigations.

References

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