CVE-2026-13426 is a medium-severity (CVSS 5.4) Path Traversal vulnerability in github.com/mattermost/mattermost/server/public. A fix is available for github.com/mattermost/mattermost/server/public — see the affected versions and patch details below.
github.com/mattermost/mattermost/server/public vulnerable to path traversal in API route construction
Exploitation Status
No confirmed exploitation observed yet
- 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-2026-13426.
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/publicReal-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
The Mattermost Go module github.com/mattermost/mattermost/server/public versions < v0.1.22 fail to validate path parameters when constructing API route paths which allows an attacker to redirect API calls to unintended endpoints via crafted IDs containing path traversal components. Mattermost Advisory ID: MMSA-2025-00532
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/mattermost/mattermost/server/public | all versions | 0.1.22go get github.com/mattermost/mattermost/server/public@v0.1.22 |
Detection & 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/public, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/mattermost/mattermost/server/public to 0.1.22 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-13426 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
Frequently Asked Questions
Is CVE-2026-13426 in your dependencies?
Find it across Go, including transitive dependencies.