CVE-2026-107804: Nginx UI: Bundled reverse proxy can bypass IP allowlists and enable shared login lockout
Summary
In Nginx UI versions 2.2.0 through 2.5.x, the official bundled reverse-proxy topology did not preserve the external client identity used by Gin. The backend treated the local proxy peer as the client because no trusted proxy was configured, while the proxy supplied the actual address in forwarding headers.
Impact
This has two distinct effects in bundled-proxy deployments:
IP allowlist enforcement: management API requests forwarded by the bundled proxy were identified as loopback and could pass the loopback exception even when the external source was not in the configured allowlist. Protected management operations still required valid credentials; this did not grant unauthenticated administrator access. Login availability: failed login attempts from different external sources were attributed to one loopback address. An unauthenticated attacker could therefore trigger the shared temporary login-ban threshold and deny password or OTP login to other users behind the proxy until the ban expired. Existing authenticated sessions were not invalidated.
Remediation
Upgrade to Nginx UI 2.6.0 or later. The fix explicitly trusts only the intended bundled proxy, validates configured trusted proxies, uses the resolved client address consistently, and fails closed when an IP allowlist is enabled but the client address is invalid.
Fix commit: https://github.com/0xJacky/nginx-ui/commit/e30e331303fc21cf077a2bea724bd79e66892eaf
Other sources
Nginx UI is a web user interface for the Nginx web server. From 2.2.0 until 2.6.0, the bundled reverse proxy does not preserve the external client identity used by Gin because the backend has no trusted proxy configuration. Management requests can be attributed to loopback and pass the IP allowlist loopback exception, although valid credentials are still required. Failed logins from different external clients are also attributed to the same loopback address, allowing an unauthenticated attacker to trigger a shared temporary login ban for password or OTP authentication without invalidating existing sessions. This issue is fixed in version 2.6.0.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/0xJacky/Nginx-UIto a version that resolves this vulnerability.Fixed in 1.9.10-0.20260904075558-e30e331303fc - Upgrade
Upgrade
Nginx UIto a version that resolves this vulnerability.Fixed in 2.6.0
Event History
Frequently Asked Questions
Who is exposed to the IP allowlist bypass?
Deployments using the bundled reverse proxy in affected versions are exposed where management access relies on an IP allowlist and its loopback exception. An attacker still needs valid credentials to access management functions.
What can an unauthenticated attacker do?
They can submit failed password or OTP login attempts that are attributed to the shared loopback address. This can trigger a temporary login ban affecting other external clients, but it does not invalidate existing sessions.
Which versions are affected and what version fixes the issue?
Versions from 2.2.0 until 2.6.0 are affected. The issue is fixed in version 2.6.0.