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CVE-2026-18223
Mattermost invitation tokens not bound to invited email address allowing unauthorized team and private channel access
Medium5.0EPSS 0.16%
- Published
- Updated
- Reserved
- Assigned by
- Mattermost
Description
Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to validate the invited recipient's email address when redeeming team and guest invitation tokens, which allows an authenticated attacker to join a team or gain unauthorized access to private channels via a forwarded or leaked invitation link.. Mattermost Advisory ID: MMSA-2026-00747
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| MattermostCNA (assigner) | 3.1 | Medium5.0 | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N |
| NVDNVD · Analyzed | 3.1 | Medium5.0 | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.16% · top 95% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.0.
Weakness
Affected products
- affected 11.10.0 – ≤ 11.10.0
- affected 11.7.0 – ≤ 11.7.9
- affected 11.9.0 – ≤ 11.9.1
- affected 11.8.0 – ≤ 11.8.5
- unaffected 11.11.0
- unaffected 11.10.1
- unaffected 11.7.10
- unaffected 11.9.2
- unaffected 11.8.6
What to do
Solution: Update Mattermost to versions 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 or higher.
References (1)
- MMSA-2026-00747 (opens in a new tab)vendor-advisory
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-18223)Record last updated .