CVE-2026-48743
Envoy: HTTP/3 to HTTP/1 request smuggling via headers-only request with nonzero Content-Length
At a glance
- Source
- NVD
- EPSS
- EPSS 0.30 % · percentile 22 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Analyzed
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.
Weaknesses (CWE)
- CWE-444 — HTTP Request/Response Smuggling
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N | GitHub_M |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N | NVD · security-advisories@github.com (Secondary) |
European references
- ENISA EUVD · EUVD-2026-39822
- GCVE · GCVE-0-2026-48743
Affected configurations (NVD CPE)
cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*≥ 1.35.0 < 1.35.13cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*≥ 1.36.0 < 1.36.9cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*≥ 1.37.0 < 1.37.5cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*≥ 1.38.0 < 1.38.3
Affected products
| Product | Versions |
|---|---|
| envoyproxy · envoy | affected >= 1.38.0, < 1.38.1 ; affected >= 1.37.0, < 1.37.3 ; affected >= 1.36.0, < 1.36.7 ; affected >= 1.35.0, < 1.35.11 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |