CVE-2026-48743
Description
A flaw was found in Envoy, an open source edge and service proxy. This vulnerability occurs when Envoy translates an HTTP/3 request that is complete at the transport layer but still carries a nonzero Content-Length into an HTTP/1 request for an upstream server. If the upstream server responds before fully reading the declared body, a subsequent Envoy-generated request can be misinterpreted as part of the previous one. This can lead to a request desynchronization, allowing an attacker to bypass security policies and access unauthorized resources.
Statement
This is an Important flaw in Envoy, affecting Red Hat OpenShift Service Mesh and cloud.redhat.com deployments. The vulnerability arises from improper handling of HTTP/3 to HTTP/1 request translation, where a complete HTTP/3 request with a non-zero Content-Length can lead to request desynchronization on the upstream HTTP/1 server. This desynchronization allows an attacker to bypass security policies, potentially gaining unauthorized access to internal resources or services.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Changed | N/A | Changed |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N
Understanding the Weakness (CWE)
Integrity,Non-Repudiation,Access Control
Technical Impact: Unexpected State; Hide Activities; Bypass Protection Mechanism
An attacker could create HTTP messages to exploit a number of weaknesses including 1) the message can trick the web server to associate a URL with another URL's webpage and caching the contents of the webpage (web cache poisoning attack), 2) the message can be structured to bypass the firewall protection mechanisms and gain unauthorized access to a web application, and 3) the message can invoke a script or a page that returns client credentials (similar to a Cross Site Scripting attack).
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