CVE-2024-39839
Remote username set to an arbitrary string by remote user
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow users to set their own remote username, when shared channels were enabled, which allows a user on a remote to set their remote username prop to an arbitrary string, which would be then synced to the local server as long as the user hadn't been synced before.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Remote username set to an arbitrary string by remote user
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow users to set their own remote username, when shared channels were enabled, which allows a user on a remote to set their remote username prop to an arbitrary string, which would be then synced to the local server as long as the user hadn't been synced before.
- Record
CVE-2024-39839- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
EUVDEUVD-2024-2663
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow users to set their own remote username, when shared channels were enabled, which allows a user on a remote to set their remote username prop to an arbitrary string, which would be then synced to the local server as long as the user hadn't been synced before.
- Record
EUVD-2024-2663- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-vg6q-84p8-qvqh
Mattermost allows a user on a remote to set their remote username prop to an arbitrary string
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow users to set their own remote username, when shared channels were enabled, which allows a user on a remote to set their remote username prop to an arbitrary string, which would be then synced to the local server as long as the user hadn't been synced before.
- Record
GHSA-vg6q-84p8-qvqh- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N - CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/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, 9.8.x <= 9.8.1 fail to disallow users to set their own remote username, when shared channels were enabled, which allows a user on a remote to set their remote username prop to an arbitrary string, which would be then synced to the local server as long as the user hadn't been synced before.
- Record
CVE-2024-39839- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
OSV
Remote username set to an arbitrary string by remote user
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow users to set their own remote username, when shared channels were enabled, which allows a user on a remote to set their remote username prop to an arbitrary string, which would be then synced to the local server as long as the user hadn't been synced before.
- Record
CVE-2024-39839- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
OSVGHSA-vg6q-84p8-qvqh
Mattermost allows a user on a remote to set their remote username prop to an arbitrary string
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow users to set their own remote username, when shared channels were enabled, which allows a user on a remote to set their remote username prop to an arbitrary string, which would be then synced to the local server as long as the user hadn't been synced before.
- Record
GHSA-vg6q-84p8-qvqh- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N - CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-284
- Updated
- 2026-11-02
OSVBIT-mattermost-2024-39839 No score
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow users to set their own remote username, when shared channels were enabled, which allows a user on a remote to set their remote username prop to an arbitrary string, which would be then synced to the local server as long as the user hadn't been synced before.
- Record
BIT-mattermost-2024-39839- Updated
- 2026-11-02
OSVGO-2024-3024 No score
Mattermost allows a user on a remote to set their remote username prop to an arbitrary string in github.com/mattermost/mattermost-server
Mattermost allows a user on a remote to set their remote username prop to an arbitrary string in github.com/mattermost/mattermost-server
- Record
GO-2024-3024- 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 |
mattermostBitnami |
9.5.0 up to 9.5.7, 9.7.0 up to 9.7.6, 9.8.0 up to 9.8.2, 9.9.0 to 9.9.0 | 9.5.79.7.69.8.2 |
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-2024-39839 is a medium vulnerability (CVSS 4.3) 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.