CVE-2026-48743
Envoy: HTTP/3 to HTTP/1 request smuggling via headers-only request with nonzero Content-Length
Description
Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, Envoy can translate a downstream HTTP/3 request that is complete at the transport layer (HEADERS with FIN / headers-only close) but still carries a nonzero Content-Length into a complete upstream HTTP/1 request with unresolved body debt. In an HTTP/1 upstream deployment where the origin replies before reading the declared body and keeps the connection reusable, the beginning of the next Envoy-generated upstream request can be consumed as the first request's body. The remaining bytes are then parsed by the origin as a new HTTP/1 request. This was reproduced as a route-bypass/desync: direct /pwn was denied by Envoy, but the second downstream H3 stream received the response for backend-parsed GET /pwn HTTP/1.1. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.
INFO
Published Date :
June 26, 2026, 6:17 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 | HIGH | MITRE-CVE | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update Envoy to version 1.35.11 or later.
- Update Envoy to version 1.36.7 or later.
- Update Envoy to version 1.37.3 or later.
- Update Envoy to version 1.38.1 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-2026-48743.
| URL | Resource |
|---|---|
| https://github.com/envoyproxy/envoy/security/advisories/GHSA-8phg-2h2q-jgxf | Exploit Vendor Advisory Mitigation |
| https://github.com/envoyproxy/envoy/security/advisories/GHSA-8phg-2h2q-jgxf | Exploit Vendor Advisory Mitigation |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-48743 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-2026-48743
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-2026-48743 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-48743 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. Antes de 1.35.11, 1.36.7, 1.37.3 y 1.38.1, Envoy puede traducir una solicitud HTTP/3 descendente que está completa en la capa de transporte (HEADERS con FIN / cierre solo de encabezados) pero que aún lleva una Content-Length distinta de cero en una solicitud HTTP/1 ascendente completa con deuda de cuerpo no resuelta. En una implementación ascendente HTTP/1 donde el origen responde antes de leer el cuerpo declarado y mantiene la conexión reutilizable, el comienzo de la siguiente solicitud ascendente generada por Envoy puede ser consumido como el cuerpo de la primera solicitud. Los bytes restantes son entonces analizados por el origen como una nueva solicitud HTTP/1. Esto se reprodujo como un bypass de ruta/desincronización: el /pwn directo fue denegado por Envoy, pero el segundo flujo H3 descendente recibió la respuesta para el GET /pwn HTTP/1.1 analizado por el backend. Esta vulnerabilidad está corregida en 1.35.11, 1.36.7, 1.37.3 y 1.38.1. -
Initial Analysis by [email protected]
Jun. 29, 2026
Action Type Old Value New Value 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) 1.35.0 up to (excluding) 1.35.13 Added Reference Type GitHub, Inc.: https://github.com/envoyproxy/envoy/security/advisories/GHSA-8phg-2h2q-jgxf Types: Exploit, Mitigation, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/envoyproxy/envoy/security/advisories/GHSA-8phg-2h2q-jgxf Types: Exploit, Mitigation, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 29, 2026
Action Type Old Value New Value Added Reference https://github.com/envoyproxy/envoy/security/advisories/GHSA-8phg-2h2q-jgxf Added SSVC {'id': 'CVE-2026-48743', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-29T15:04:55.378026Z'} -
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, < 1.38.1'}, {'status': 'affected', 'version': '>= 1.37.0, < 1.37.3'}, {'status': 'affected', 'version': '>= 1.36.0, < 1.36.7'}, {'status': 'affected', 'version': '>= 1.35.0, < 1.35.11'}]}] Added Description Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, Envoy can translate a downstream HTTP/3 request that is complete at the transport layer (HEADERS with FIN / headers-only close) but still carries a nonzero Content-Length into a complete upstream HTTP/1 request with unresolved body debt. In an HTTP/1 upstream deployment where the origin replies before reading the declared body and keeps the connection reusable, the beginning of the next Envoy-generated upstream request can be consumed as the first request's body. The remaining bytes are then parsed by the origin as a new HTTP/1 request. This was reproduced as a route-bypass/desync: direct /pwn was denied by Envoy, but the second downstream H3 stream received the response for backend-parsed GET /pwn HTTP/1.1. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N Added CWE CWE-444 Added Reference https://github.com/envoyproxy/envoy/security/advisories/GHSA-8phg-2h2q-jgxf