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Fencer Vulns
low 3.7

CVE-2025-64763 json

Envoy forwards early CONNECT data in TCP proxy mode

published 2025-12-03 11 mo ago modified 2026-09-08 2 mo ago also BIT-envoy-2025-64763 , EUVD-2025-201099 , GHSA-rj35-4m94-77jh

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/envoyproxy/envoy 1.33.13, 1.34.11, 1.35.7, 1.36.3
  • bitnami envoy 1.33.13, 1.34.11, 1.35.7, 1.36.3
  • envoyproxy envoy 1.33.13, 1.34.11, 1.35.7, 1.36.3

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-64763 updated cvss 5.3

Envoy: Envoy: De-synchronized CONNECT tunnel state due to early data handling in TCP proxy mode

  • Red Hat OpenShift Service Mesh 2 openshift-service-mesh/pilot-rhel8, openshift-service-mesh/grafana-rhel8, openshift-service-mesh/proxyv2-rhel9, openshift-service-mesh/istio-cni-rhel8, openshift-service-mesh/ratelimit-rhel8, openshift-service-mesh/istio-rhel8-operator, +2 more Red Hat OpenShift Service Mesh 3 openshift-service-mesh/istio-cni-rhel9, openshift-service-mesh/istio-pilot-rhel9, openshift-service-mesh/istio-proxyv2-rhel9, openshift-service-mesh/istio-ztunnel-rhel9, openshift-service-mesh/istio-rhel9-operator, openshift-service-mesh/istio-must-gather-rhel9, +3 more
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
11 mo ago

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
GitHub 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
go github.com/envoyproxy/envoy
>=1.36.0, <1.36.3
>=1.35.0, <1.35.7
>=1.34.0, <1.34.11
<1.33.13
1.36.3
1.35.7
1.34.11
1.33.13
bitnami envoy
<1.33.13
>=1.34.0, <1.34.11
>=1.35.0, <1.35.7
>=1.36.0, <1.36.3
1.33.13
1.34.11
1.35.7
1.36.3

Affected products

  • envoyproxy envoy

Classification

Weakness
  • CWE-693 Protection Mechanism Failure

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.