What is CVE-2018-16851?

CVE-2018-16851 is a medium-severity vulnerability in Samba, classified under NULL Pointer Dereference. CVSS score: 6.5/10. Published 2018-11-28.

How severe is CVE-2018-16851?

Medium severity. CVSS v3 base score is 6.5 out of 10.

NULL pointer dereference in Samba

CVE-2018-16851

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.

Published 2018-11-28 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.033 (87.9th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 88th percentile — 87.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.033 · newest: 0.033 · change: 0.000

Affected products

Samba
[Unknown] Samba — versions 4.9.3, 4.8.7, 4.7.12
Canonical Ubuntu Linux — versions 12.04, 14.04, 16.04
Debian Linux — versions 8.0, 9.0

Weakness classification (CWE)

CWE-476 — NULL Pointer Dereference

References

www.securityfocus.com/bid/106027 (VDB Entry, Third Party Advisory, vdb-entry)
usn.ubuntu.com/3827-2/ (vendor-advisory, Third Party Advisory)
usn.ubuntu.com/3827-1/ (vendor-advisory, Third Party Advisory)
security.netapp.com/advisory/ntap-20181127-0001/ (Third Party Advisory)
lists.debian.org/debian-lts-announce/2018/12/msg00005.html (mailing-list, Mailing List, Third Party Advisory)
bugzilla.redhat.com/show_bug.cgi (Third Party Advisory, Issue Tracking)
www.debian.org/security/2018/dsa-4345 (vendor-advisory, Third Party Advisory)
www.samba.org/samba/security/CVE-2018-16851.html (Patch, Vendor Advisory)
security.gentoo.org/glsa/202003-52 (vendor-advisory, Third Party Advisory)

Frequently asked questions

What is CVE-2018-16851?: CVE-2018-16851 is a medium-severity vulnerability in Samba, classified under NULL Pointer Dereference. CVSS score: 6.5/10. Published 2018-11-28.
How severe is CVE-2018-16851?: Medium severity. CVSS v3 base score is 6.5 out of 10.