External risk intelligence

Echo Proxy Middleware Allows Authentication Bypass

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-118264

The vulnerability resides in the Proxy middleware of the Echo Go web framework, which is commonly utilized to build internet-facing web applications, APIs, and gateway services. Because the flaw specifically impacts how the framework handles proxy routing and WebSocket connections, it is frequently exposed in typical deployments where these applications serve public traffic.

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability in the Echo web framework could allow unauthorized access to systems by bypassing authentication or authorization controls. This occurs when the framework mishandles specific WebSocket upgrade requests, potentially forwarding subsequent traffic directly to an upstream server without proper routing. The primary concern is confirming if our environment utilizes this framework and is exposed to this specific configuration.

Bypasses web framework security controls.
Matters for systems handling sensitive data.
Confirm framework use and exposure.

Attack Path

How an attacker could exploit the issue

An attacker could begin by accessing a deployed application that uses the vulnerable Echo framework. If the application has a proxy route, the attacker might be able to send a specially crafted WebSocket upgrade request. When the upstream server rejects this upgrade, subsequent regular HTTP requests might bypass Echo's routing and middleware, potentially reaching sensitive endpoints.

Accessible proxy route required.
WebSocket upgrade rejection triggers bypass.
Bypassed authentication or authorization.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an unauthenticated attacker to bypass access controls on specific routes by manipulating WebSocket upgrade requests. When the configured upstream rejects a WebSocket upgrade, subsequent HTTP requests on that connection may be forwarded directly to the upstream, bypassing Echo's router and any middleware, including authentication or authorization checks, under specific conditions including an accessible proxy route and a cooperating rejected-upgrade response.

Bypass authentication or authorization.
An accessible proxy route is needed.
Unauthorized access to protected resources.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Echo Go web framework's Proxy middleware is susceptible to bypassing authentication or authorization controls. Application owners and platform teams are likely responsible for addressing this, starting with identifying all deployments of the affected Echo versions, confirming their exposure and business criticality, and then prioritizing remediation.

Application owners should manage the issue.
Verify proxy route accessibility and upstream.
Plan remediation based on risk assessment.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

Free EASM Trial See How Signal Works

Frequently asked questions

What is the Echo framework and how is it used?

Echo is a high-performance, minimalist web framework built for the Go programming language. Developers use it to construct web applications, RESTful APIs, and microservices. It is particularly popular for building gateway services that route traffic to various backend systems, often acting as the front door for complex, distributed architectures.

What does CVE-2026-118264 mean for security?

This vulnerability involves improper request handling, specifically classified as CWE-444 (Inconsistent Interpretation) and CWE-863 (Incorrect Authorization). It means the Echo framework can fail to properly route traffic after a specific connection state occurs. This failure effectively ignores security controls like authentication checks that would normally protect your backend routes.

How is this authentication bypass triggered?

An attacker must target an exposed proxy route with a WebSocket upgrade request that the upstream server rejects. Crucially, the bug is not triggered by a standard successful WebSocket connection; it specifically requires the upstream to send a non-WebSocket response. If this occurs, subsequent HTTP traffic flows directly to the backend, skipping the Echo framework's security logic entirely.

Do I need to worry if my Echo application is internal?

Halo Surface Signal indicates this flaw is most likely to be triggered in internet-facing deployments where proxy routing and public traffic interact. While internal applications are technically susceptible if the conditions are met, the risk is significantly higher for services directly exposed to the public internet, where attackers can freely attempt these specific WebSocket upgrade sequences.

How do I start fixing this Echo vulnerability?

Begin by auditing your dependency manifests to identify if your services are using Echo versions between 4.0.0 and 4.16.1 or any 5.x version before 5.4.1. Once identified, prioritize updating to Echo 4.16.1 or 5.4.1. If you cannot update immediately, evaluate if your proxy routes truly require WebSocket functionality and consider restricting or disabling these paths to mitigate the risk of exploitation.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.