CVE-2026-59900
Description
A flaw was found in Netty's netty-codec-http2 component. The HTTP/2 encoder does not properly handle special characters in HTTP headers. This vulnerability allows a remote attacker to craft specific HTTP/2 requests, leading to HTTP response splitting and header injection attacks. Such attacks can enable an attacker to manipulate web content or inject malicious headers.
Statement
A flaw was found in Netty's HTTP/2 codec (netty-codec-http2). The HTTP/2 encoder fails to properly neutralize special characters in HTTP headers, allowing an attacker to craft specially formed HTTP/2 requests that inject arbitrary header content. This can lead to HTTP response splitting and header injection attacks. The issue is fixed in versions 4.1.136.Final and 4.2.16.Final.
Mitigation
- Upgrade `netty-codec-http2` to version 4.1.136.Final (4.1.x branch) or 4.2.16.Final (4.2.x branch).
- If upgrading is not immediately possible, ensure that HTTP/2 traffic is routed through a reverse proxy or WAF that validates and sanitizes HTTP headers before forwarding to the Netty-based application.
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 | 6.5 | 5.3 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | Low | None | N/A |
| Integrity Impact | High | Low | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Understanding the Weakness (CWE)
Integrity,Access Control
Technical Impact: Modify Application Data; Gain Privileges or Assume Identity
CR and LF characters in an HTTP header may give attackers control of the remaining headers and body of the message that the application intends to send/receive, as well as allowing them to create additional messages entirely under their control.
Frequently Asked Questions
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