# CVE-2025-64763: Envoy forwards early CONNECT data in TCP proxy mode

Source: https://junglewise.ai/threats/cve-2025-64763-envoy-forwards-early-connect-data-in-tcp-proxy-mode  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-12-05  
License: CC BY 4.0 with a link back

CVE-2025-64763 · Severity: low · CVSS 3.1 · Published 2025-12-05

Envoy forwards early CONNECT data in TCP proxy mode

Technologies: [github.com/envoyproxy/envoy (Go)](https://junglewise.ai/threats/technologies/github-com-envoyproxy-envoy). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2025-64763 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-64763 being exploited in the wild.

**How severe is CVE-2025-64763?** Low severity, with a CVSS score of 3.1, published 5 December 2025.

**Which products and versions are affected?** github.com/envoyproxy/envoy (Go) SEMVER:introduced=1.36.0,fixed=1.36.3.

**Is there a fix for CVE-2025-64763?** Yes. github.com/envoyproxy/envoy (Go): upgrade to 1.36.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2025-64763?** Check whether you run github.com/envoyproxy/envoy (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/envoyproxy/envoy (Go): upgrade to 1.36.3 or later

  ```sh
  go get github.com/envoyproxy/envoy@v1.36.3
  ```


## Affected products

- github.com/envoyproxy/envoy (Go) SEMVER:introduced=1.36.0,fixed=1.36.3

## Identifiers

- CVE-2025-64763
- GHSA-rj35-4m94-77jh

## Related threats

- [Envoy's global rate limit may crash when the response phase limit is enabled and the response phase request is failed directly](https://junglewise.ai/threats/cve-2026-26330-envoy-s-global-rate-limit-may-crash-when-the-response-phase-limit)
- [Envoy: HTTP - filter chain execution on reset streams causing UAF crash](https://junglewise.ai/threats/cve-2026-26311-envoy-http-filter-chain-execution-on-reset-streams-causing-uaf)
- [Envoy affected by off-by-one write in JsonEscaper::escapeString()](https://junglewise.ai/threats/cve-2026-26309-envoy-affected-by-off-by-one-write-in-jsonescaper-escapestring)
- [Envoy RBAC header validation bypass via multi-value concatenation](https://junglewise.ai/threats/cve-2026-26308-envoy-rbac-header-validation-bypass-via-multi-value-concatenation)
- [Envoy vulnerable to crash for scoped ip address during DNS](https://junglewise.ai/threats/cve-2026-26310-envoy-vulnerable-to-crash-for-scoped-ip-address-during-dns)