CVE-2026-59900
Published:July 29, 2026
Updated:August 04, 2026
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.
Affected Packages
io.netty:netty-codec-http2 (JAVA):
Affected version(s) >=4.1.0.Final <4.1.136.FinalFix Suggestion:
Update to version 4.1.136.Finalio.netty:netty-codec-http2 (JAVA):
Affected version(s) >=4.1.0.Beta4 <4.1.136.FinalFix Suggestion:
Update to version 4.1.136.Finalio.netty:netty-codec-http2 (JAVA):
Affected version(s) >=4.2.0.Final <4.2.16.FinalFix Suggestion:
Update to version 4.2.16.FinalRelated Resources (6)
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Contact UsCVSS v4
Base Score:
6.9
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
LOW
Subsequent System Integrity
LOW
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.2
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
EPSS
Base Score:
0.29