CVE-2024-39274
Malicious remote can add users to arbitrary teams and channels
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Malicious remote can add users to arbitrary teams and channels
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
- Record
CVE-2024-39274- CVSS 3.1
- 8.7 High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
EUVDEUVD-2024-2562
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
- Record
EUVD-2024-2562- CVSS 3.1
- 8.7 High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-cmc8-222c-vqp9
Mattermost failed to properly validate that the channel that comes from the sync message is a shared channel
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
- Record
GHSA-cmc8-222c-vqp9- CVSS 4.0
- 9.3 Critical
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 - CVSS 3.1
- 8.7 High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
NVD
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
- Record
CVE-2024-39274- CVSS 3.1
- 8.7 High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
OSV
Malicious remote can add users to arbitrary teams and channels
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
- Record
CVE-2024-39274- CVSS 3.1
- 8.7 High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
OSVGHSA-cmc8-222c-vqp9
Mattermost failed to properly validate that the channel that comes from the sync message is a shared channel
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
- Record
GHSA-cmc8-222c-vqp9- CVSS 4.0
- 9.3 Critical
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 - CVSS 3.1
- 8.7 High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
OSVGO-2024-3028 No score
Mattermost failed to properly validate that the channel that comes from the sync message is a shared channel in github.com/mattermost/mattermost-server
Mattermost failed to properly validate that the channel that comes from the sync message is a shared channel in github.com/mattermost/mattermost-server
- Record
GO-2024-3028- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
github.com/mattermost/mattermost/server/v8Go |
9.5.0 up to 9.5.7 | 9.5.7 |
github.com/mattermost/mattermost/server/v8Go |
9.7.0 up to 9.7.6 | 9.7.6 |
github.com/mattermost/mattermost/server/v8Go |
9.8.0 up to 9.8.2 | 9.8.2 |
github.com/mattermost/mattermost/server/v8Go |
9.9.0 to 9.9.0 | 9.9.1 |
github.com/mattermost/mattermost/server/v8Go |
9.9.0 up to 9.9.1 | 9.9.1 |
github.com/mattermost/mattermost-serverGo |
9.5.0+incompatible up to 9.5.7+incompatible, 9.7.0+incompatible up to 9.7.6+incompatible, 9.8.0+incompatible up to 9.8.2+incompatible, 9.9.0+incompatible up to 9.9.1+incompatible | 9.5.7+incompatible9.7.6+incompatible9.8.2+incompatible9.9.1+incompatible |
github.com/mattermost/mattermost-server/v5Go |
All versions | None known |
github.com/mattermost/mattermost-server/v6Go |
All versions | None known |
github.com/mattermost/mattermost/server/v8Go |
All versions | None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2024-39274 is a high vulnerability (CVSS 8.7) in Mattermost, published August 1, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.34%, the 27th percentile. Fixed in github.com/mattermost/mattermost/server/v8 9.5.7.