CVE-2026-33638 is a medium-severity (CVSS 5.3) CWE-862 vulnerability in github.com/lin-snow/ech0. A fix is available for github.com/lin-snow/ech0 — see the affected versions and patch details below.
Ech0 authenticated user-list exposed data via public `/api/allusers` endpoint
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33638.
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/lin-snow/ech0Real-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
Summary
A public access-control flaw allows unauthenticated users to retrieve the full user list from GET /api/allusers. This exposes user profile metadata to anyone who can reach the application and enables remote user enumeration.
Details
The vulnerable route is registered as a public endpoint:
internal/router/user.go:17appRouterGroup.PublicRouterGroup.GET("/allusers", h.UserHandler.GetAllUsers())
However, the handler appears to have been intended as an authenticated endpoint:
internal/handler/user/user.go:177-185- API annotations indicate an authentication requirement via
@Security ApiKeyAuth
- API annotations indicate an authentication requirement via
This creates a mismatch between the documented security model and the actual routing configuration. As a result, requests to GET /api/allusers succeed without authentication and return user records, including profile metadata such as usernames, email addresses, role-related flags, avatar values, and locale information.
A negative control against another endpoint that correctly requires authentication further supports that this exposure is unintended: GET /api/user returns 401 Unauthorized when no token is supplied, while GET /api/allusers remains publicly accessible.
Impact
- Type: Access control bypass / unauthenticated data exposure
- Who is impacted: Any deployment exposing the API to untrusted networks, and all users whose profile metadata is returned by the endpoint
- Security impact: Enables remote user enumeration and disclosure of user profile metadata, which may facilitate account reconnaissance, phishing, and targeted credential attacks
- Attack preconditions: None beyond network access to the affected API endpoint
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/lin-snow/ech0 | all versions | 1.4.8-0.20260322121226-acbf1fd71011go get github.com/lin-snow/ech0@v1.4.8-0.20260322121226-acbf1fd71011 |
Affected Products
ech0ech0Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/lin-snow/ech0, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/lin-snow/ech0 to 1.4.8-0.20260322121226-acbf1fd71011 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33638 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2026-33638 in your dependencies?
Find it across Go, including transitive dependencies.