GHSA-mxq2-5jpg-7474 CVE-2026-6062 GO-2026-6484
Mattermost doesn't validate channel ownership of an existing subscription before applying edits
- Severity
- 6.4 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.24%
- Chance of exploitation in the next 30 days. Higher than 15.11% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-639 Authorization Bypass Through User-Controlled Key
- Fix
11.7.1- Upgrade github.com/mattermost/mattermost-server to this version or later
Description
Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 Fail to validate channel ownership of an existing subscription before applying edits which allows an authenticated attacker to hijack subscriptions from channels they have no access to via a crafted PUT request to the subscription edit endpoint.. Mattermost Advisory ID: MMSA-2026-00650
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| github.com/mattermost/mattermost-server | >= 11.7.0, < 11.7.1 |
11.7.1 |
| github.com/mattermost/mattermost-server | >= 11.6.0, < 11.6.3 |
11.6.3 |
| github.com/mattermost/mattermost-server | >= 11.5.0, < 11.5.6 |
11.5.6 |
| github.com/mattermost/mattermost-server | >= 10.11.0, < 10.11.18 |
10.11.18 |
| github.com/mattermost/mattermost-server | >= 10.11.0+incompatible, < 10.11.18+incompatible>= 11.5.0+incompatible, < 11.5.6+incompatible>= 11.6.0+incompatible, < 11.6.3+incompatible>= 11.7.0+incompatible, < 11.7.1+incompatible |
10.11.18+incompatible11.5.6+incompatible11.6.3+incompatible11.7.1+incompatible |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
github.com/mattermost/mattermost-server Go → 11.7.1
- go
go get github.com/mattermost/mattermost-server@v11.7.1 && go mod tidy
Severity breakdown
CVSS 3.1 6.4
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- Low
- Availability
- Low
Weakness
CWE-639: Authorization Bypass Through User-Controlled Key
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
How to prevent it
- Architecture and Design: For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
- Architecture and Design, Implementation: Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
- Architecture and Design: Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-xmfh-3ccg-c9fx Mattermost has an Incorrect Authorization issue | Low | Also affects github.com/mattermost/mattermost-server |
| GHSA-h998-hxxj-8q83 Mattermost doesn't invalidate cached authentication state for active WebSocket connections during global session revocation | Medium | Also affects github.com/mattermost/mattermost-server |
| GHSA-g5vr-6pgg-74qv Mattermost doesn't enforce bot-specific permission checks on the user active status endpoint | Low | Also affects github.com/mattermost/mattermost-server |
| GHSA-jqgv-39mg-7c2r Mattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret | Medium | Also affects github.com/mattermost/mattermost-server |
| GHSA-2g8v-grq3-hq2g Mattermost doesn't enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler | Medium | Also affects github.com/mattermost/mattermost-server |
| GHSA-6hxm-w4hv-vgvw Mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints | High | Also affects github.com/mattermost/mattermost-server |
| GHSA-9p44-r552-4wp9 Mattermost doesn't sanitize the Remote Cluster API response on PATCH operations | Medium | Also affects github.com/mattermost/mattermost-server |
| GHSA-8qq9-cqj8-82w4 Mattermost doesn't sanitize FileInfo.Name received from federated peers during shared channel file sync | High | Also affects github.com/mattermost/mattermost-server |
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