---
title: "CVE-2018-16851\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2018-16851?format=md
keywords: index, follow
---

# CVE-2018-16851

Publication date 27 November 2018

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**6.5 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2018-16851?format=md#impact-score)

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## Description

Samba from version 4.0.0 and before versions 4.7.12, 4.8.7, 4.9.3 is
vulnerable to a denial of service. During the processing of an LDAP search
before Samba's AD DC returns the LDAP entries to the client, the entries
are cached in a single memory object with a maximum size of 256MB. When
this size is reached, the Samba process providing the LDAP service will
follow the NULL pointer, terminating the process. There is no further
vulnerability associated with this issue, merely a denial of service.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| samba | 18.10 cosmic | Fixed 2:4.8.4+dfsg-2ubuntu2.1 |
| 18.04 LTS bionic | Fixed 2:4.7.6+dfsg~ubuntu-0ubuntu2.5 |
| 16.04 LTS xenial | Fixed 2:4.3.11+dfsg-0ubuntu0.16.04.18 |
| 14.04 LTS trusty | Fixed 2:4.3.11+dfsg-0ubuntu0.14.04.19 |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

6.5 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Privileges required | Low |
  | User interaction | None |
  | Scope | Unchanged |
  | Confidentiality impact | None |
  | Integrity impact | None |
  | Availability impact | High |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.5 · Medium |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-16851)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2018-16851)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2018-16851)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2018-16851)

### Related Ubuntu Security Notices (USN)

+ [USN-3827-2](https://usn.ubuntu.com/USN-3827-2)
+ Samba vulnerabilities
+ 27 November 2018

+ [USN-3827-1](https://usn.ubuntu.com/USN-3827-1)
+ Samba vulnerabilities
+ 27 November 2018

### Other references

* <https://www.samba.org/samba/security/CVE-2018-16851.html>
* <https://www.cve.org/CVERecord?id=CVE-2018-16851>