How severe is GHSA-cxf3-9h37-7rr8?

No CVSS score has been assigned to GHSA-cxf3-9h37-7rr8 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-cxf3-9h37-7rr8?

GHSA-cxf3-9h37-7rr8 affects the following packages: github.com/labstack/echo/v4 (Go), github.com/labstack/echo/v5 (Go). Ecosystems affected: Go.

How do I fix GHSA-cxf3-9h37-7rr8?

Update github.com/labstack/echo/v4 to 4.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cxf3-9h37-7rr8 is resolved across your whole dependency graph.

How do I detect GHSA-cxf3-9h37-7rr8 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/labstack/echo/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-cxf3-9h37-7rr8 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-cxf3-9h37-7rr8 actively exploited in the wild?

No public exploit code has been indexed for GHSA-cxf3-9h37-7rr8 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-cxf3-9h37-7rr8 published, and has it been updated?

GHSA-cxf3-9h37-7rr8 was published on October 23, 2026 and was last updated on October 23, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

Echo: Rejected WebSocket upgrades can bypass Echo route-level access controlsGHSA-cxf3-9h37-7rr8

Fix: labstack/echo@1855061

GHSA-cxf3-9h37-7rr8 is a security vulnerability in github.com/labstack/echo/v4. A fix is available for github.com/labstack/echo/v4 — see the affected versions and patch details below.

Published

Oct 23, 2026

Updated

Oct 23, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 23, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

2 pkgs affected

🐹github.com/labstack/echo/v4🐹github.com/labstack/echo/v5

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Impact

Echo's Proxy middleware selected a raw tunnel when the client requested a WebSocket upgrade, before validating whether the configured upstream accepted it. If the upstream returned an ordinary HTTP response and kept the connection alive, subsequent HTTP requests on that connection were forwarded directly to the same upstream without passing through Echo's router or route-specific middleware.

This can bypass authentication or authorization enforced only at Echo's routes. Exploitation requires an accessible proxy route, an upstream that rejects the upgrade without closing the connection, and a target resource on that upstream without independent authorization. The issue does not provide arbitrary-host proxying or bypass the upstream's own authentication.

Affected versions and patch

The raw proxy implementation is present throughout the v4 and v5 release lines up to v4.16.0 and v5.4.0. Runtime reproductions confirmed v4.15.0, v4.16.0, v5.0.0 and v5.4.0; source history also shows the missing upgrade-response validation in v4.0.0.

Upgrade to v4.16.1 or v5.4.1. The patch routes WebSocket upgrades through Go's HTTP reverse proxy and enters a tunnel only after a valid upstream upgrade response. Rejected upgrades remain ordinary HTTP requests.

Fix commits: v4, v5.

Workarounds

Reject WebSocket upgrade requests before they reach affected Echo proxy routes, or enforce authorization independently at every upstream resource. Merely returning a non-101 response from the upstream does not prevent the vulnerable raw tunnel.

Credits

Reported by @Duodum.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/labstack/echo/v4`	≥ 4.0.0&&< 4.16.1	4.16.1`go get github.com/labstack/echo/v4@v4.16.1`
🐹Go	`github.com/labstack/echo/v5`	≥ 5.0.0&&< 5.4.1	5.4.1`go get github.com/labstack/echo/v5@v5.4.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/labstack/echo/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/labstack/echo/v4 to 4.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cxf3-9h37-7rr8 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

## Impact Echo's Proxy middleware selected a raw tunnel when the client requested a WebSocket upgrade, before validating whether the configured upstream accepted it. If the upstream returned an ordinary HTTP response and kept the connection alive, subsequent HTTP requests on that connection were forwarded directly to the same upstream without passing through Echo's router or route-specific middleware. This can bypass authentication or authorization enforced only at Echo's routes. Exploitation requires an accessible proxy route, an upstream that rejects the upgrade without closing the connect

O3 Security · Impact-Aware SCA

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