# Envoy Proxy denial-of-service in HTTP filter with prefix_rewrite

Source: https://junglewise.ai/threats/gcp-2026-067-0c826055  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-12. Updated: 2026-10-12  
License: CC BY 4.0 with a link back

Severity: info · Published 2026-10-12

Envoy Proxy, a widely-used network proxy component in Google Cloud Service Mesh, contains a denial-of-service vulnerability when HTTP filters modify request headers after route selection. An attacker can crash or disable the proxy by crafting specific requests, potentially disrupting service availability for applications relying on Cloud Service Mesh.

Technologies: [Envoy Proxy](https://junglewise.ai/threats/technologies/envoy), [Google Cloud Platform](https://junglewise.ai/threats/technologies/google-cloud-platform). Vendors: [Envoy Proxy](https://junglewise.ai/threats/vendors/envoy-proxy), [Google](https://junglewise.ai/threats/vendors/google).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Informational severity, published 12 October 2026.

**Which products and versions are affected?** Envoy Proxy Envoy Proxy.

**Is there a fix for This vulnerability?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is This vulnerability attacked?** It is attacked over the network, in a hosted service.

**Am I affected?** Check whether you run Envoy Proxy or Google Cloud Platform. 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.

## Technical details

A DoS vulnerability exists in Envoy Proxy when an HTTP filter such as ext_proc with route_cache_action: RETAIN mutates the :path header after route selection on a route configured with prefix_rewrite. The vulnerability requires network access and specific filter configuration. Exploitation causes denial of service.

## Affected products

- Envoy Proxy Envoy Proxy

## Timeline

- 2026-10-12: disclosed

## References

- [https://docs.cloud.google.com/support/bulletins/index](https://docs.cloud.google.com/support/bulletins/index)

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