# Mattermost vulnerabilities & exploitation

> As of 2026-10-05, Threadlinqs tracks 5 Mattermost CVEs, 0 in the CISA Known Exploited Vulnerabilities catalog, linked to 0 tracked threat campaigns.

**Data as of:** 2026-10-05

## Exploitation timeline

Threadlinqs has recorded 5 Mattermost CVEs published between 2026-06-15 and 2026-08-15. The busiest month was 2026-08 (4 new CVEs). None of them is listed in CISA KEV yet.

## Most exploited vulnerabilities

Ranked with CISA KEV listings first, then EPSS exploit probability, then CVSS score. Showing 5 of 5 tracked Mattermost CVEs.

- [CVE-2026-9859](https://intel.threadlinqs.com/cve/CVE-2026-9859) — MEDIUM 6.5 · EPSS 0.3% · 2026-08-17
- [CVE-2026-9816](https://intel.threadlinqs.com/cve/CVE-2026-9816) — HIGH 8.3 · EPSS 0.2% · 2026-08-17
- [CVE-2026-8823](https://intel.threadlinqs.com/cve/CVE-2026-8823) — LOW 3.8 · EPSS 0.2% · 2026-06-22
- [CVE-2026-75587](https://intel.threadlinqs.com/cve/CVE-2026-75587) — LOW 3.6 · EPSS 0.1% · 2026-08-17
- [CVE-2026-9693](https://intel.threadlinqs.com/cve/CVE-2026-9693) — LOW 3.5 · 2026-08-17

## Products affected

Threadlinqs normalises CPE and CNA product records across all 5 CVEs; 1 distinct Mattermost product is affected. The most frequently affected:

- Mattermost — 5 CVEs

## Threat activity

No tracked threat campaign references Mattermost products or CVEs yet. Vulnerability records are still monitored for exploitation and linked as campaigns are ingested.

## How to prioritise Mattermost patching

This order follows the data Threadlinqs holds for Mattermost, not a generic severity checklist:

- No Mattermost CVE is in CISA KEV yet, so rank by exploit probability instead.
- Outside KEV, the highest EPSS scores are [CVE-2026-9859](https://intel.threadlinqs.com/cve/CVE-2026-9859) (0.3%), [CVE-2026-9816](https://intel.threadlinqs.com/cve/CVE-2026-9816) (0.2%), [CVE-2026-8823](https://intel.threadlinqs.com/cve/CVE-2026-8823) (0.2%).
- 0 CVEs score Critical and 1 High on CVSS v3 (maximum 8.3, average 5.1); sequence these after KEV and high-EPSS items.

## About this data

Vendor attribution comes from the CNA and CPE product records of each CVE, folded to one vendor name; CVSS, EPSS and KEV status are read from the Threadlinqs CVE catalog; campaign and actor links come from tracked threat records. Counts reflect the data as of 2026-10-05 and refresh daily.

Canonical: https://intel.threadlinqs.com/vendors/mattermost
All vendors: https://intel.threadlinqs.com/vendors
Full detection coverage and IOCs via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp