No exploitation reported

CVE-2019-5456

Q: Is CVE-2019-5456 actively exploited?

Active exploitation of CVE-2019-5456 has not been confirmed. Its EPSS score was 1.3% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2019-5456?

CVE-2019-5456 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2019-07-30
WeaknessCWE-255 · CWE-300

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

SMTP MITM refers to a malicious actor setting up an SMTP proxy server between the UniFi Controller version <= 5.10.21 and their actual SMTP server to record their SMTP credentials for malicious use later.

Timeline

dates in UTC

2019-07-3021:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2019-5456?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2019-5456?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Ui unifi controller

Branch	Affected	Fixed in	Source
5.10	≤ 5.10.21	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

community.ui.comRelease Notes · Vendor Advisory
community.ui.comRelease Notes · Vendor Advisory
community.ui.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.18.1read 2026-10-23
NVDCVSS 2.04.3read 2026-10-23
CNAweakness (CWE)CWE-300read 2026-10-23
NVDweakness (CWE)CWE-255read 2026-10-23
FIRST EPSSEPSS score1.3 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2019-07-30
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2019-5456?

Is CVE-2019-5456 actively exploited?

Active exploitation of CVE-2019-5456 has not been confirmed. Its EPSS score was 1.3% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2019-5456?

CVE-2019-5456 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

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