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20Track

Echo: Rejected WebSocket upgrades can bypass Echo route-level access controls

labstack echo · CVE-2026-118264 ETK-2026-2898 EUVD-2026-112396 GHSA-CXF3-9H37-7RR8
0 news outlets0 CERTs and agencies1 research labs

Assessment: Track

SSVC decision points: exploitation none, automatable no, technical impact total, deployment low.

What is it?

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.

Evidence

Technical advisories1Detailed write-ups from security research teams

Exploitation

  • Exploit code published (not verified by us)
  • Exploited in the wild (confirmed by a source)
  • Listed as known exploited (CISA KEV)
CVSS
9.1
EPSS
–
First seen
2 h ago
Status
confirmed

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