Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, Netty's HTTP/2-to-HTTP/1.x translation layer (`Http2StreamFrameToHttpObjectCodec` and `InboundHttp2ToHttpAdapter`) fails to deduplicate or validate `Host` headers when an HTTP/2 client supplies both the `:authority` pseudo-header and a literal `host` header in a single HEADERS frame. The translator maps `:authority` to `Host` and separately copies the literal `host` header, producing an `HttpRequest` object containing two `Host` headers with attacker-controlled differing values. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.
History

Wed, 29 Jul 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 29 Jul 2026 18:15:00 +0000

Type Values Removed Values Added
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. Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, Netty's HTTP/2-to-HTTP/1.x translation layer (`Http2StreamFrameToHttpObjectCodec` and `InboundHttp2ToHttpAdapter`) fails to deduplicate or validate `Host` headers when an HTTP/2 client supplies both the `:authority` pseudo-header and a literal `host` header in a single HEADERS frame. The translator maps `:authority` to `Host` and separately copies the literal `host` header, producing an `HttpRequest` object containing two `Host` headers with attacker-controlled differing values. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.
Title io.netty/netty-codec-http2: Netty: Improper header neutralization in netty-codec-http2 Netty codec-http2: Lack of Host Header Deduplication in HTTP/2→HTTP/1.x Translation Leads to Request Routing Bypass
Weaknesses CWE-444
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N'}


Tue, 28 Jul 2026 00:15:00 +0000

Type Values Removed Values Added
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.
Title io.netty/netty-codec-http2: Netty: Improper header neutralization in netty-codec-http2
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N'}

threat_severity

Moderate


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-29T18:07:24.906Z

Reserved: 2026-07-07T16:40:07.984Z

Link: CVE-2026-59900

cve-icon Vulnrichment

Updated: 2026-07-29T18:07:16.627Z

cve-icon NVD

No data.

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-07-09T00:00:00Z

Links: CVE-2026-59900 - Bugzilla

cve-icon OpenCVE Enrichment

No data.