Unauthorized users can trigger interactive post actions in private channels via action cookie channel mismatch in Mattermost
Published Jul 13, 2026
6.5
MEDIUMCVSS 3.1
EPSS 0.30%
Description
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to verify that the channel referenced in an action cookie matches the channel of the target post, which allows an authenticated user without access to a private channel to trigger interactive post actions on posts in that channel via a cookie obtained from any accessible channel.. Mattermost Advisory ID: MMSA-2026-00690
Affected products
-
- Version 10.11.0StatusaffectedConstraints<=10.11.19
- Version 11.6.0StatusaffectedConstraints<=11.6.4
- Version 11.7.0StatusaffectedConstraints<=11.7.2
- Version 10.11.20StatusunaffectedConstraints-
- Version 11.6.5StatusunaffectedConstraints-
- Version 11.7.3StatusunaffectedConstraints-
- Version 11.8.0StatusunaffectedConstraints-
- Version
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mattermost | Mattermost | unaffected |
|
- ≥ 10.11.0 · < 10.11.20
- ≥ 11.6.0 · < 11.6.5
- ≥ 11.7.0 · < 11.7.3
No data.
No Red Hat product state for this CVE.
No package ranges for this CVE.
Remediation
Vendor solution
Update Mattermost to versions 11.8.0, 11.7.3, 11.6.5, 10.11.20 or higher.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
No CVSS v3.0 score for this CVE.
No CVSS v2.0 score for this CVE.
This CVE is not in the KEV list.
CISA SSVC (Vulnrichment)
Stakeholder-Specific Vulnerability Categorization from CISA ADP.
Exploitation
NoneAutomatable
NoTechnical Impact
PartialDecision
n/aAssessed Jul 13, 2026 · SSVC 2.0.3
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 2, 2026.
Score over time
Jul–Oct 2026- EPSS v5
Percentile over time
- EPSS v5
Table of values (2 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 2, 2026 | 0.30% (0.00299) | 20.54th | v5 (v2026.06.15) |
| Jul 13, 2026 | 0.17% (0.00174) | 7.10th | v5 (v2026.06.15) |
References (1)
- https://mattermost.com/security-updates vendor-advisoryVendor Advisory
| Link | Providers | Tags |
|---|---|---|
| https://mattermost.com/security-updates | vendor-advisoryVendor Advisory |
Change history (0)
No recorded changes yet.