CVE-2023-1776 — mattermost-server
HIGHCVE-2023-1776 is a high-severity (CVSS 7.3) Cross-site Scripting (XSS) vulnerability in github.com/mattermost/mattermost-server/v6. A fix is available for github.com/mattermost/mattermost-server/v6 — see the affected versions and patch details below.
Stored XSS via SVG attachment on Boards
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-1776.
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/v6🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server/v5🐹github.com/mattermost/mattermost-server/v6Real-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
Boards in Mattermost allows an attacker to upload a malicious SVG image file as an attachment to a card and share it using a direct link to the file.
Issue Identifier: MMSA-2023-00139
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost-server/v6 | ≥ 6.0.0&&< 7.1.6 | 7.1.6go get github.com/mattermost/mattermost-server/v6@v7.1.6 |
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 7.7.0&&< 7.7.2 | 7.7.2go get github.com/mattermost/mattermost-server@v7.7.2 |
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 7.1.0&&< 7.1.6 | 7.1.6go get github.com/mattermost/mattermost-server@v7.1.6 |
| 🐹Go | github.com/mattermost/mattermost-server | ≥ 7.8.0&&< 7.8.1 | 7.8.1go get github.com/mattermost/mattermost-server@v7.8.1 |
| 🐹Go | github.com/mattermost/mattermost-server/v5 | ≥ 5.0.0&&< 7.1.6 | 7.1.6go get github.com/mattermost/mattermost-server/v5@v7.1.6 |
| 🐹Go | github.com/mattermost/mattermost-server/v6 | ≥ 3.3.0&&< 7.1.6 | 7.1.6go get github.com/mattermost/mattermost-server/v6@v7.1.6 |
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/v6, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/mattermost/mattermost-server/v6 to 7.1.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-1776 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2023-1776 in your dependencies?
Find it across Go, including transitive dependencies.