Summary
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.
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.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
CVE-2026-39386 has a CVSS score of 8.8 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.0.11, 0.0.0-20260406184107-c54bcf1ee211); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
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.
Frequently Asked Questions
- What is CVE-2026-39386? CVE-2026-39386 is a high-severity improper input validation vulnerability in github.com/m1k1o/neko/server (go), affecting versions >= 3.0.0, < 3.0.11. It is fixed in 3.0.11, 0.0.0-20260406184107-c54bcf1ee211. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is CVE-2026-39386? CVE-2026-39386 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/m1k1o/neko/server are affected by CVE-2026-39386? github.com/m1k1o/neko/server (go) versions >= 3.0.0, < 3.0.11 is affected.
- Is there a fix for CVE-2026-39386? Yes. CVE-2026-39386 is fixed in 3.0.11, 0.0.0-20260406184107-c54bcf1ee211. Upgrade to this version or later.
- Is CVE-2026-39386 exploitable, and should I be worried? Whether CVE-2026-39386 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-39386 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-39386?
- Upgrade
github.com/m1k1o/neko/serverto 3.0.11 or later - Upgrade
github.com/m1k1o/neko/serverto 0.0.0-20260406184107-c54bcf1ee211 or later
- Upgrade