CVE-2025-64763: Envoy forwards early CONNECT data in TCP proxy mode
envoyproxy · envoy
Affected: envoyproxy · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 25% of scored CVEs
DescriptionCVE.org
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.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- envoyproxy · envoy>= 1.36.0, <= 1.36.2; >= 1.35.0, <= 1.35.6; >= 1.34.0, <= 1.34.10; <= 1.33.12
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- envoyproxy
- Published
- December 2025
CoverageNo articles yet
No CyberSIXT article names CVE-2025-64763 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.