CVE-2026-47221
Envoy: Null pointer deref in internal redirects
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.
INFO
Published Date :
June 26, 2026, 6:16 p.m.
Last Modified :
Oct. 25, 2026, 5:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | MITRE-CVE | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update Envoy to version 1.35.13 or later.
- Update Envoy to version 1.36.9 or later.
- Update Envoy to version 1.37.5 or later.
- Update Envoy to version 1.38.3 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-47221.
| URL | Resource |
|---|---|
| https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr | Exploit Vendor Advisory |
| https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-47221 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-47221
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-47221 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-47221 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 25, 2026
Action Type Old Value New Value Added Translation Title: envoy de envoyproxy, Description: Envoy es un proxy de borde y de servicio de código abierto diseñado para aplicaciones nativas de la nube. Desde 1.18.0 hasta 1.35.13, 1.36.9, 1.37.5 y 1.38.3, el filtro del router contiene una vulnerabilidad de desreferencia de puntero nulo al manejar redirecciones internas HTTP 303 (Ver Otros) para solicitudes sin cuerpo que no son GET/HEAD. Cuando una solicitud POST, PUT, DELETE o PATCH sin cuerpo se envía a una ruta configurada con una política de redirección interna que incluye 303 en redirect_response_codes, y el origen responde con HTTP 303, el código de manejo de redirección intenta vaciar un búfer de cuerpo de solicitud que nunca fue asignado. Esto resulta en un fallo de segmentación que bloquea todo el proceso de Envoy. Cuando una ruta configurada con internal_redirect_policy que incluye 303 en redirect_response_codes y el origen debe devolver una respuesta HTTP 303, un atacante no autenticado puede explotar esto para causar una denegación de servicio completa, terminando todas las conexiones activas. Esta vulnerabilidad se corrige en 1.35.13, 1.36.9, 1.37.5 y 1.38.3. -
Initial Analysis by [email protected]
Jun. 27, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.37.0 up to (excluding) 1.37.5 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.38.0 up to (excluding) 1.38.3 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.36.0 up to (excluding) 1.36.9 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.18.0 up to (excluding) 1.35.13 Added Reference Type GitHub, Inc.: https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr Types: Exploit, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 26, 2026
Action Type Old Value New Value Added Reference https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr Added SSVC {'id': 'CVE-2026-47221', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-26T18:33:10.549936Z'} -
New CVE Received by [email protected]
Jun. 26, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'envoyproxy', 'product': 'envoy', 'versions': [{'status': 'affected', 'version': '>= 1.38.0, < 1.38.3'}, {'status': 'affected', 'version': '>= 1.37.0, < 1.37.5'}, {'status': 'affected', 'version': '>= 1.36.0, < 1.36.9'}, {'status': 'affected', 'version': '>= 1.18.0, < 1.35.13'}]}] Added 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. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-476 Added Reference https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr