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Envoy CVE-2025-64763

| EUVDEUVD-2025-201099 LOW
Protection Mechanism Failure (CWE-693)
2025-12-03 security-advisories@github.com GHSA-rj35-4m94-77jh
3.7
CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY
3.7 LOW
AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Lifecycle Timeline

4
EUVD ID Assigned
Mar 15, 2026 - 16:14 euvd
EUVD-2025-201099
Analysis Generated
Mar 15, 2026 - 16:14 vuln.today
Patch released
Mar 15, 2026 - 16:14 nvd
Patch available
CVE Published
Dec 03, 2025 - 18:15 nvd
LOW 3.7

DescriptionGitHub Advisory

Envoy is a high-performance edge/middle/service proxy. In 1.33.12, 1.34.10, 1.35.6, 1.36.2, and earlier, when Envoy is configured in TCP proxy mode to handle CONNECT requests, it accepts client data before issuing a 2xx response and forwards that data to the upstream TCP connection. If a forwarding proxy upstream from Envoy then responds with a non-2xx status, this can cause a de-synchronized CONNECT tunnel state. By default Envoy continues to allow early CONNECT data to avoid disrupting existing deployments. The envoy.reloadable_features.reject_early_connect_data runtime flag can be set to reject CONNECT requests that send data before a 2xx response when intermediaries upstream from Envoy may reject establishment of a CONNECT tunnel.

Analysis

Envoy is a high-performance edge/middle/service proxy. In 1.33.12, 1.34.10, 1.35.6, 1.36.2, and earlier, when Envoy is configured in TCP proxy mode to handle CONNECT requests, it accepts client data before issuing a 2xx response and forwards that data to the upstream TCP connection. If a forwarding proxy upstream from Envoy then responds with a non-2xx status, this can cause a de-synchronized CONNECT tunnel state. By default Envoy continues to allow early CONNECT data to avoid disrupting existing deployments. The envoy.reloadable_features.reject_early_connect_data runtime flag can be set to reject CONNECT requests that send data before a 2xx response when intermediaries upstream from Envoy may reject establishment of a CONNECT tunnel.

Technical ContextAI

This vulnerability is classified as Protection Mechanism Failure (CWE-693).

RemediationAI

A vendor patch is available. Apply it as soon as possible and verify the fix.

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Vendor StatusVendor

Debian

Bug #987544
envoyproxy
Release Status Fixed Version Urgency
open - -

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CVE-2025-64763 vulnerability details – vuln.today

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