CVE-2017-18895 is a medium-severity (CVSS 5.3) Information Exposure vulnerability in github.com/mattermost/mattermost-server. A fix is available for github.com/mattermost/mattermost-server — see the affected versions and patch details below.
Mattermost Server exposes sensitive user status information via REST API version 4 endpoint
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-serverReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
An issue was discovered in Mattermost Server before 4.2.0, 4.1.1, and 4.0.5. It allows attackers to obtain sensitive information (user statuses) via a REST API version 4 endpoint.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost-server | all versions | 4.0.5go get github.com/mattermost/mattermost-server@v4.0.5 |
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 4.1.0&&< 4.1.1 | 4.1.1go get github.com/mattermost/mattermost-server@v4.1.1 |
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 4.2.0-rc1&&< 4.2.0 | 4.2.0go get github.com/mattermost/mattermost-server@v4.2.0 |
Affected Products
mattermost servermattermostDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/mattermost/mattermost-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/mattermost/mattermost-server to 4.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-18895 is resolved across your whole dependency graph.
Workarounds
Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.
Frequently Asked Questions
Is CVE-2017-18895 in your dependencies?
Find it across Go, including transitive dependencies.