CVE-2026-118264: Request Smuggling

Description

Echo is a Go web framework. From 4.0.0 until 4.16.1 and 5.4.1, Echo's Proxy middleware selects a raw tunnel from a client WebSocket upgrade request before verifying that the configured upstream accepted the upgrade. If the upstream rejects the upgrade with an ordinary keep-alive response, later HTTP requests on the connection are sent directly to that upstream without passing through Echo's router or route-specific middleware. This can bypass authentication or authorization enforced only by Echo routes, but requires an accessible proxy route, a cooperating rejected-upgrade response, and a target without independent upstream authorization. This issue is fixed in 4.16.1 and 5.4.1.

Is your site exposed to CVE-2026-118264?

Run a free security scan — no signup, results in seconds.

Weakness Type (CWE)

CWE-444 CWE-444

CWE-863 Incorrect Authorization

References

Other References

https://github.com/labstack/echo/commit/1855061e572ae9dab727c811d8382f266bfbaaec https://github.com/labstack/echo/commit/3fb0ba7e17645bb65611e2a08875d0a2f65c421f https://github.com/labstack/echo/releases/tag/v4.16.1 https://github.com/labstack/echo/releases/tag/v5.4.1 https://github.com/labstack/echo/security/advisories/GHSA-cxf3-9h37-7rr8

Frequently Asked Questions

What is CVE-2026-118264? +

Echo is a Go web framework. From 4.0.0 until 4.16.1 and 5.4.1, Echo's Proxy middleware selects a raw tunnel from a client WebSocket upgrade request before verifying that the configured upstream accepted the upgrade. If the upstream rejects the upgrade with an ordinary keep-alive response, later HTTP requests on the connection are sent directly to that upstream without passing through Echo's router or route-specific middleware. This can bypass authentication or authorization enforced only by Echo routes, but requires an accessible proxy route, a cooperating rejected-upgrade response, and a target without independent upstream authorization. This issue is fixed in 4.16.1 and 5.4.1.

How do I check if I'm vulnerable to CVE-2026-118264? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-1867

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in ithewei libhv allows HTTP Response Smuggling.This issue affects libhv: through …

CVE-2024-23316

HTTP request desynchronization in Ping Identity PingAccess, all versions prior to 8.0.1 affected allows an attacker to send specially crafted …

CVE-2024-38494

This vulnerability allows a high-privileged authenticated PAM user to achieve remote command execution on the affected PAM system by sending …

CVE-2025-6999

An HTTP Request Smuggling [CWE-444] vulnerability in the Authentication portal of WatchGuard Fireware OS allows a remote attacker to evade …

CVE-2025-11915

Connection desynchronization between an HTTP proxy and the model backend. The fixes were rolled out for all proxies in front …

CVE-2023-53878

Member Login Script 3.3 contains a client-side desynchronization vulnerability that allows attackers to manipulate HTTP request handling by exploiting Content-Length …

CVE-2026-118264