CVE-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
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/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
Impact
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.
Patches
The vulnerability has been patched in the following releases:
Users should upgrade to v3.0.11 or later (for the 3.0 branch) or v3.1.2 or later.
Workarounds
If upgrading is not immediately possible, the following mitigations can reduce risk:
- Restrict access to trusted users only (avoid granting accounts to untrusted parties)
- Run the instance only when needed; avoid leaving it continuously exposed
- Disable or restrict access to the
/api/profileendpoint if feasible - Monitor for suspicious privilege changes or unexpected administrative actions
Note: These are temporary mitigations and do not fully eliminate the vulnerability. Upgrading is strongly recommended.
Credits
Neko thanks @blitzkrieg-patch for responsibly disclosing this vulnerability and reaching out directly. This contribution helped strengthen the project, and the whole community benefits from it.
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 |
Affected Products
nekom1k1oDetection & 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
Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable.
Frequently Asked Questions
Is CVE-2026-39386 in your dependencies?
Find it across Go, including transitive dependencies.