---
title: "CVE-2024-39274: Mattermost failed to properly validate that the channel that comes from the sync message is a shared channel"
url: https://erroneo.us/security/cve/CVE-2024-39274/
description: "CVE-2024-39274 (github.com/mattermost/mattermost/server/v8 (Go)): Mattermost versions 9.9.x"
type: vulnerability-record
section: "Security Digest"
date_published: 2024-08-01
date_modified: 2024-11-18
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2024-39274"
kev: false
cvss: 9.3
epss: 0.00341
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2024-39274: Mattermost failed to properly validate that the channel that comes from the sync message is a shared channel

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.3% , percentile 26: FIRST’s model estimates a 0.3% chance of exploitation activity in the next 30 days, higher than 26% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Needs an account (high (admin)). Exposure depends on who can log in.
- Only applies if your dependency tree includes github.com/mattermost/mattermost/server/v8 (Go) >= 9.5.0, < 9.5.7, fixed in 9.5.7 ; github.com/mattermost/mattermost/server/v8 (Go) >= 9.7.0, < 9.7.6, fixed in 9.7.6 ; github.com/mattermost/mattermost/server/v8 (Go) >= 9.8.0, < 9.8.2, fixed in 9.8.2 ; github.com/mattermost/mattermost/server/v8 (Go) = 9.9.0, fixed in 9.9.1 . Check your lockfile, including transitive dependencies.

## What it is

Mattermost versions 9.9.x

## Affected packages

- Go `github.com/mattermost/mattermost/server/v8` >= 9.5.0, < 9.5.7 → fixed: 9.5.7
- Go `github.com/mattermost/mattermost/server/v8` >= 9.7.0, < 9.7.6 → fixed: 9.7.6
- Go `github.com/mattermost/mattermost/server/v8` >= 9.8.0, < 9.8.2 → fixed: 9.8.2
- Go `github.com/mattermost/mattermost/server/v8` = 9.9.0 → fixed: 9.9.1

## Affected products (CVE record)

- Mattermost Mattermost: 9.9.0, 9.5.0 <= 9.5.6, 9.7.0 <= 9.7.5, 9.8.0 <= 9.8.1

## Severity

- Mattermost CVSS 3.1: 8.7 `CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N`
- GitHub CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.34% probability of exploitation activity in the next 30 days; percentile 26.

## Sources

- [GitHub Advisory GHSA-cmc8-222c-vqp9](https://github.com/advisories/GHSA-cmc8-222c-vqp9)
- [CVE.org record CVE-2024-39274](https://www.cve.org/CVERecord?id=CVE-2024-39274)
- [NVD entry CVE-2024-39274](https://nvd.nist.gov/vuln/detail/CVE-2024-39274)
- [mattermost.com](https://mattermost.com/security-updates)
- [pkg.go.dev](https://pkg.go.dev/vuln/GO-2024-3028)

---
Source page: https://erroneo.us/security/cve/CVE-2024-39274/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt