CVE-2025-58056
Description
A flaw in Netty’s HTTP/1.1 chunked encoding parser allows newline (LF) characters in chunk extensions to be incorrectly treated as the end of the chunk-size line instead of requiring the proper CRLF sequence. This discrepancy can be exploited in rare cases where a reverse proxy interprets the same input differently, potentially enabling HTTP request smuggling attacks such as bypassing access controls or corrupting responses.
Statement
This issue is considered Moderate rather than Important because successful exploitation depends on a very specific deployment condition: the presence of an intermediary reverse proxy that both mishandles lone LF characters in chunk extensions and forwards them unmodified to Netty. By itself, Netty’s parsing quirk does not introduce risk, and in most real-world environments, reverse proxies normalize or reject malformed chunked requests, preventing smuggling. As a result, the vulnerability has limited reach, requires a niche configuration to be exploitable, and does not universally expose Netty-based servers to request smuggling—hence it is rated moderate in severity rather than important or critical.
Mitigation
To mitigate this issue, enforce strict RFC compliance on all front-end proxies and load balancers so that lone LF characters in chunk extensions are rejected or normalized before being forwarded. Additionally, configure input validation at the application or proxy layer to block malformed chunked requests, ensuring consistent parsing across all components in the request path.
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 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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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