Inconsistent interpretation of HTTP requests in envoy - CVE-2026-48743
Published: June 24, 2026
Vulnerability identifier: #VU135110
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-48743
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Cloud Native Computing Foundation
Affected software:
envoy
envoy
Detailed vulnerability description
The vulnerability allows a remote attacker to smuggle requests and bypass routing or policy controls.
The vulnerability exists due to inconsistent interpretation of http requests in the downstream HTTP/3 to upstream HTTP/1 translation boundary when processing a headers-only HTTP/3 request with a nonzero Content-Length. A remote attacker can send a specially crafted HTTP/3 request to smuggle requests and bypass routing or policy controls.
Exploitation requires downstream HTTP/3 to be enabled, an upstream HTTP/1 origin that can respond before consuming the declared request body, and reuse of the upstream HTTP/1 connection after that response.
How to mitigate CVE-2026-48743
Install security update from vendor's website.