CVE-2026-47221 Envoy: Null pointer deref in internal redirects
An unauthenticated attacker can crash the Envoy proxy by sending specific body-less requests to routes configured for 303 internal redirects.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47221?
CVE-2026-47221 is a medium-severity vulnerability in Envoyproxy Envoy, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.18.0 until 1.35.13, 1.36.9, 1.37.5, and 1.38.3, the router filter contains a null pointer dereference vulnerability when handling HTTP 303 (See Other) internal redirects for body-less non-GET/HEAD requests. When a POST, PUT, DELETE, or PATCH request without a body is sent to a route configured with internal redirect policy that includes 303 in redirect_response_codes, and the upstream responds with HTTP 303, the redirect handling code attempts to drain a request body buffer that was never allocated. This results in a segmentation fault that crashes the entire Envoy process. When route configured with internal_redirect_policy including 303 in redirect_response_codes and upstream must return HTTP 303 response, an unauthenticated attacker can exploit this to cause complete denial of service, terminating all active connections. This vulnerability is fixed in 1.35.13, 1.36.9, 1.37.5, and 1.38.3.
Weakness: CWE-476
Which versions are affected by CVE-2026-47221?
1 open source package ship an affected version, including envoy. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
envoy Bitnami | From 1.18.0 | 1.35.13, 1.36.9, 1.37.5, 1.38.3 |
Products include Envoyproxy Envoy.
How do I fix CVE-2026-47221?
Upgrade envoy to a fixed version for your release line: 1.35.13, 1.36.9, 1.37.5 or 1.38.3.
Is CVE-2026-47221 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47221 exists.
Other vulnerabilities in Envoyproxy Envoy
Sources
Also known as BIT-envoy-2026-47221, GHSA-rcff-gw58-pjpr.