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Fencer Vulns
high 8.8

CVE-2026-39386 json

Neko has Self-service Privilege Escalation for Authenticated Users

published 2026-04-21 6 mo ago modified 2026-10-26 13 d ago also GHSA-2gw9-c2r2-f5qf , GO-2026-4960 , EUVD-2026-24027

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/m1k1o/neko/server 0.0.0-20260406184107-c54bcf1ee211, 3.0.11
  • m1k1o neko 3.0.11, 3.1.2
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
6 mo ago

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
GitHub 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
go github.com/m1k1o/neko/server
>=3.0.0, <3.0.11
>=0.0.0-20250322225643-212bf8a60756, <0.0.0-20260406184107-c54bcf1ee211
>=0.0.0-20250326225119-51bbad7650d3, <0.0.0-20260406184107-c54bcf1ee211
3.0.11
0.0.0-20260406184107-c54bcf1ee211

Affected products

  • m1k1o neko

Classification

Weakness
  • CWE-20 Improper Input Validation
  • CWE-269 Improper Privilege Management
  • CWE-284 Improper Access Control
  • CWE-639 Authorization Bypass Through User-Controlled Key
  • CWE-862 Missing Authorization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.