Protection Mechanism Failure Affecting envoyproxy/envoy package, versions [1.8.0, 1.33.13)[1.34.0, 1.34.11)[1.35.0,1.35.7)[1.36.0,1.36.3)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-UNMANAGED-ENVOYPROXYENVOY-14176096
- published4 Dec 2025
- disclosed3 Dec 2025
- creditPatrick Smith
Introduced: 3 Dec 2025
CVE-2025-64763 (opens in a new tab)How to fix?
Upgrade envoyproxy/envoy to version 1.33.13, 1.34.11, 1.35.7, 1.36.3 or higher.
Overview
Affected versions of this package are vulnerable to Protection Mechanism Failure in the handling of TCP proxy mode. An attacker can cause a desynchronized tunnel state between the proxy and upstream servers by sending data for a CONNECT request before a 2xx response is issued, which is then forwarded upstream even if the tunnel is not successfully established.
Notes:
- To prevent disruption to existing deployments, early CONNECT data will still be allowed. Fixing this vulnerability requires setting the
envoy.reloadable_features.reject_early_connect_dataruntime flag to true after updating.