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CVE-2023-42670: Samba: ad dc busy rpc multiple listener dos

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-11-03 · updated 2026-06-17
• Weakness: CWE-400

Description

A flaw was found in Samba. It is susceptible to a vulnerability where multiple incompatible RPC listeners can be initiated, causing disruptions in the AD DC service. When Samba's RPC server experiences a high load or unresponsiveness, servers intended for non-AD DC purposes (for example, NT4-emulation "classic DCs") can erroneously start and compete for the same unix domain sockets. This issue leads to partial query responses from the AD DC, causing issues such as "The procedure number is out of range" when using tools like Active Directory Users. This flaw allows an attacker to disrupt AD DC services.

Affected products

• Fedoraproject Fedora: 39
• Samba: before 4.17.12; from 4.18.0 before 4.18.8; from 4.19.0 before 4.19.1 — fixed in 4.17.12, 4.18.8, 4.19.1

How to fix

Upgrade to a fixed version: Samba 4.17.12, 4.18.8, 4.19.1. Check the vendor advisory for mitigations.

References

• https://access.redhat.com/security/cve/CVE-2023-42670
• https://bugzilla.redhat.com/show_bug.cgi?id=2241885
• https://bugzilla.samba.org/show_bug.cgi?id=15473
• https://www.samba.org/samba/security/CVE-2023-42670.html
• https://access.redhat.com/security/cve/CVE-2023-42670
• https://bugzilla.redhat.com/show_bug.cgi?id=2241885
• https://bugzilla.samba.org/show_bug.cgi?id=15473
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZUMVALLFFDFC53JZMUWA6HPD7HUGAP5I/
• https://security.netapp.com/advisory/ntap-20231124-0002/
• https://www.samba.org/samba/security/CVE-2023-42670.html

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