GHSA-mp6x-97xj-9x62 CVE-2025-12421 GO-2025-4170
Mattermost fails to to verify the token used during code exchange
- Severity
- 9.9 / 10
- Critical · CVSS 3.1
- Exploit chance (EPSS)
- 0.45%
- Chance of exploitation in the next 30 days. Higher than 38.78% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Fix
- Available
- 2 packages have a fixed version
Description
Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| github.com/mattermost/mattermost-server | >= 11.0.0, < 11.0.3 |
11.0.3 |
| github.com/mattermost/mattermost-server | >= 10.12.0, < 10.12.2 |
10.12.2 |
| github.com/mattermost/mattermost-server | >= 10.11.0, < 10.11.5 |
10.11.5 |
| github.com/mattermost/mattermost-server | >= 10.5.0, < 10.5.13 |
10.5.13 |
| github.com/mattermost/mattermost-server | all versions |
No fix yet |
| github.com/mattermost/mattermost-server/v5 | all versions |
No fix yet |
| github.com/mattermost/mattermost-server/v6 | all versions |
No fix yet |
| github.com/mattermost/mattermost/server/v8 | < 8.0.0-20251022210333-acda1fb5dd46 |
8.0.0-20251022210333-acda1fb5dd46 |
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 → 11.0.3
- go
go get github.com/mattermost/mattermost-server@v11.0.3 && go mod tidy
github.com/mattermost/mattermost/server/v8 Go → 8.0.0-20251022210333-acda1fb5dd46
- go
go get github.com/mattermost/mattermost/server/v8@v8.0.0-20251022210333-acda1fb5dd46 && go mod tidy
Severity breakdown
CVSS 3.1 9.9
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Weakness
CWE-287: Improper Authentication
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
How to prevent it
- Architecture and Design: Use an authentication framework or library such as the OWASP ESAPI Authentication feature.
CWE-303: Incorrect Implementation of Authentication Algorithm
The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.
References
Advisories
Packages
Other links
- github.com/mattermost/mattermost/commit/5072bbf689a46b3b97b2373f26149f5891396e6b
- github.com/mattermost/mattermost/commit/acda1fb5dd46a2f46c76ae67012423c760525eaa
- github.com/mattermost/mattermost/commit/f361e7d75a7ab9df5a2106e1ceb919b94b55e41d
- github.com/mattermost/mattermost/commit/feb598ed2b7ac3cb78a253b032ad7e4628b0de00
- mattermost.com/security-updates
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-mxq2-5jpg-7474 Mattermost doesn't validate channel ownership of an existing subscription before applying edits | 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 |
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