CVE-2017-18909: mattermost mattermost_server Improper Certificate Validation
Vulnerability summary
CVE-2017-18909 is a high (CVSS 7.5) Improper Certificate Validation vulnerability in mattermost mattermost_server. EPSS estimates a 0.66% chance of exploitation in the next 30 days, higher than 51.4% of scored vulnerabilities.
Severe, CVSS 7.5 (NVD); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 2 · Related 2Timeline
- 19-06-2020PublishedVulnerability first disclosed.
- 05-08-2024Last modifiedVulnerability information updated.
Description
An issue was discovered in Mattermost Server before 3.9.0 when SAML is used. Encryption and signature verification are not mandatory.
CVSS metrics
3 scores · 2 sources · 2 versions- OSV · GoEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS trend
Probability
0.66%
Chance of exploitation in the next 30 days
Percentile
51%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.66% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Github.com/mattermost1 product
- mattermost-server< 3.8.1-0.20170504181128-4f074fed0d65 | All versions (No fix recorded)
Mattermost1 product
- mattermost_server< 3.9.0
2 vendors · 2 products
