# 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.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Jun 2026
- **Updated:** 26 Jun 2026
- **Also known as:** BIT-envoy-2026-47221, GHSA-rcff-gw58-pjpr

## 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 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-47221?

1 open source package ship an affected version, including envoy. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `envoy` | Bitnami | From 1.18.0 | 1.35.13, 1.36.9, 1.37.5, 1.38.3 |

Products: 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

- [CVE-2022-29226](https://insights.sbomify.com/CVE-2022-29226/): Trivial authentication bypass in Envoy (critical 10.0)
- [CVE-2019-18801](https://insights.sbomify.com/CVE-2019-18801/): Memory corruption in n/a (critical 9.8)
- [CVE-2019-18802](https://insights.sbomify.com/CVE-2019-18802/): Security feature bypass in n/a (critical 9.8)
- [CVE-2020-35470](https://insights.sbomify.com/CVE-2020-35470/): Information disclosure in n/a (high 8.8)
- [CVE-2024-23324](https://insights.sbomify.com/CVE-2024-23324/): Envoy ext auth can be bypassed when Proxy protocol filter sets invalid UTF-8 metadata (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47221 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47221 exists.

Affected packages and fixed versions:
- envoy (Bitnami): affected from 1.18.0; fixed in 1.35.13, 1.36.9, 1.37.5, 1.38.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-47221/ (Markdown: https://insights.sbomify.com/CVE-2026-47221/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47221
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47221
- OSV: https://osv.dev/vulnerability/CVE-2026-47221

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47221/
Summaries are generated and may contain mistakes; the official description above is the record.