CVE-2026-39386
HIGHCVE-2026-39386 is a high-severity (CVSS 8.8) Improper Input Validation vulnerability in github.com/m1k1o/neko/server. O3 Security confirms whether CVE-2026-39386 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Neko has Self-service Privilege Escalation for Authenticated Users
Blast Radius
github.com/m1k1o/neko/server🐹github.com/m1k1o/neko/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
Neko is a a self-hosted virtual browser that runs in Docker and uses WebRTC In versions 3.0.0 through 3.0.10 and 3.1.0 through 3.1.1, any authenticated user can immediately obtain full administrative control of the entire Neko instance (member management, room settings, broadcast control, session termination, etc.). This results in a complete compromise of the instance. The vulnerability has been patched in v3.0.11 and v3.1.2. If upgrading is not immediately possible, the following mitigations can reduce risk: Restrict access to trusted users only (avoid granting accounts to untrusted parties); ensure all user passwords are strong and only shared with trusted individuals; run the instance only when needed; avoid leaving it continuously exposed; place the instance behind authentication layers such as a reverse proxy with additional access controls; disable or restrict access to the /api/profile endpoint if feasible; and/or monitor for suspicious privilege changes or unexpected administrative actions. Note that these are temporary mitigations and do not fully eliminate the vulnerability. Upgrading is strongly recommended.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/m1k1o/neko/server | ≥ 3.0.0&&< 3.0.11 | 3.0.11 |
| 🐹Go | github.com/m1k1o/neko/server | ≥ 0.0.0-20250322225643-212bf8a60756&&< 0.0.0-20260406184107-c54bcf1ee211 | 0.0.0-20260406184107-c54bcf1ee211 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/m1k1o/neko/server. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/m1k1o/neko/server to 3.0.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39386 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-39386 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-39386. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-39386 in your dependencies?
O3 detects CVE-2026-39386 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.