CVE-2026-39386 — server
HIGHCVE-2026-39386 is a high-severity (CVSS 8.8) Improper Input Validation vulnerability in github.com/m1k1o/neko/server. A fix is available for github.com/m1k1o/neko/server — see the affected versions and patch details below.
Neko has Self-service Privilege Escalation for Authenticated Users
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-2026-39386.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-39386 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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 | 3.0.11go get github.com/m1k1o/neko/server@v3.0.11 |
| 🐹Go | github.com/m1k1o/neko/server | ≥ 0.0.0-20250322225643-212bf8a60756&&< 0.0.0-20260406184107-c54bcf1ee211 | 0.0.0-20260406184107-c54bcf1ee211go get github.com/m1k1o/neko/server@v0.0.0-20260406184107-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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-39386 can be triaged on real exposure rather than presence alone.
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 Security finds CVE-2026-39386 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.