Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel. Mattermost Advisory ID: MMSA-2026-00637.
Update github.com/mattermost/mattermost-server to 11.6.1; github.com/mattermost/mattermost-server to 11.5.4; github.com/mattermost/mattermost-server to 11.4.5; github.com/mattermost/mattermost-server to 10.11.15 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanMattermost doesn't archive the channel before removing persistent notifications affects github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go). Severity is medium. Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel. Mattermost Advisory ID: MMSA-2026-00637.
AI coding agents often install or upgrade packages automatically in go. A medium vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel. Mattermost Advisory ID: MMSA-2026-00637.
Update github.com/mattermost/mattermost-server to 11.6.1; github.com/mattermost/mattermost-server to 11.5.4; github.com/mattermost/mattermost-server to 11.4.5; github.com/mattermost/mattermost-server to 10.11.15 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanMattermost doesn't archive the channel before removing persistent notifications affects github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go). Severity is medium. Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel. Mattermost Advisory ID: MMSA-2026-00637.
AI coding agents often install or upgrade packages automatically in go. A medium vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| github.com/mattermost/mattermost-servergo |
|---|
| =11.6.0 |
| 11.6.1 |
| github.com/mattermost/mattermost-servergo | >=11.5.0,<11.5.4 | 11.5.4 |
|---|
| github.com/mattermost/mattermost-servergo | >=11.4.0,<11.4.5 | 11.4.5 |
|---|
| github.com/mattermost/mattermost-servergo | >=10.11.0,<10.11.15 | 10.11.15 |
|---|
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard| github.com/mattermost/mattermost-servergo |
|---|
| =11.6.0 |
| 11.6.1 |
| github.com/mattermost/mattermost-servergo | >=11.5.0,<11.5.4 | 11.5.4 |
|---|
| github.com/mattermost/mattermost-servergo | >=11.4.0,<11.4.5 | 11.4.5 |
|---|
| github.com/mattermost/mattermost-servergo | >=10.11.0,<10.11.15 | 10.11.15 |
|---|
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard