9.1

CVE-2017-18911: mattermost mattermost_server Improper Certificate Validation

CVSS: 9.1v3.1CriticalModified
AliasesGHSA-m462-mqw4-2c8mGO-2026-4464
Published 19-06-2020Last modified 05-08-2024
Open JSON

Vulnerability summary

CVE-2017-18911 is a critical (CVSS 9.1) Improper Certificate Validation vulnerability in mattermost mattermost_server. EPSS estimates a 0.67% chance of exploitation in the next 30 days, higher than 51.3% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.1/10
010
Critical · v3.1 (NVD)
EPSS score
0.67%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2 · Related 2
OPENSUSE-SU-2026:21483-1SUSE-SU-2026:0757-1

Timeline

  1. 19-06-2020
    PublishedVulnerability first disclosed.
  2. 05-08-2024
    Last modifiedVulnerability information updated.

Description

An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. The X.509 certificate validation can be skipped for a TLS-based e-mail server.

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

0.67%

Chance of exploitation in the next 30 days

Percentile

51%

Versus all other CVEs

30-day change

0.00 pp

From 0.66% on 22-09-2026

22-09-202622-10-2026
EPSS score
0.67%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Github.com/mattermost1 product
  • mattermost-server< 3.6.7-rc1 | ≥ 3.7.0, < 3.7.5 | ≥ 3.8.0, < 3.8.2 | ≥ 3.8.0+incompatible, < 3.8.2+incompatible
Mattermost1 product

2 vendors · 2 products

References

8 links