CVE-2025-0620: Samba: smbd doesn't pick up group membership changes when re-authenticating an expired smb session

Severity: medium (CVSS 4.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-06-06 · updated 2026-08-31
Weakness: CWE-552

Description

A flaw was found in Samba. The smbd service daemon does not pick up group membership changes when re-authenticating an expired SMB session. This issue can expose file shares until clients disconnect and then connect again.

Affected products

Samba: from 4.21.0 before 4.21.6; from 4.22.0 before 4.22.2 — fixed in 4.21.6, 4.22.2

How to fix

Upgrade to a fixed version: Samba 4.21.6, 4.22.2. Check the vendor advisory for mitigations.

References

https://access.redhat.com/security/cve/CVE-2025-0620
https://bugzilla.redhat.com/show_bug.cgi?id=2370453
https://www.samba.org/samba/security/CVE-2025-0620.html
http://www.openwall.com/lists/oss-security/2025/06/03/8

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