CVE-2026-42581
Description
A flaw was found in Netty's HttpObjectDecoder. A remote attacker can exploit this by sending a specially crafted HTTP/1.0 request that includes both Transfer-Encoding: chunked and Content-Length headers. While Netty correctly strips the conflicting Content-Length header for HTTP/1.1 messages, this guard is absent for HTTP/1.0. This can lead to HTTP request smuggling, where downstream proxies or handlers may misinterpret message boundaries, potentially allowing an attacker to bypass security controls or access unauthorized information.
Statement
This is an Important flaw. Netty's HttpObjectDecoder, used across various Red Hat products, improperly handles conflicting Transfer-Encoding: chunked and Content-Length headers in HTTP/1.0 requests. This allows a remote attacker to perform HTTP request smuggling, potentially bypassing security controls or gaining unauthorized access to information due to misinterpretation of message boundaries by downstream proxies or handlers.
Mitigation
To mitigate this issue, configure any reverse proxies or load balancers in front of Netty to either reject HTTP/1.0 requests containing both Transfer-Encoding: chunked and Content-Length headers, or to explicitly prioritize the Transfer-Encoding header over Content-Length for HTTP/1.0 traffic. This ensures consistent interpretation of message boundaries and prevents request smuggling attacks.
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 | 7.2 | 9.8 | 7.2 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Changed | Unchanged | Changed |
| Confidentiality | Low | High | Low |
| Integrity Impact | Low | High | Low |
| Availability Impact | None | High | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/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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