Io.netty:netty codec http2: Netty: [codec-http2] Lack of Host Header Deduplication in HTTP/2→HTTP/1.x Translation Leads to Request Routing Bypass (CVE-2026-59900)
Netty's HTTP/2-to-HTTP/1.x translation layer does not properly deduplicate or validate Host headers when both the :authority pseudo-header and a literal host header are present in a single HTTP/2 HEADERS frame. This results in an HttpRequest object containing two Host headers with differing attacker-controlled values, potentially allowing request routing bypass.
AI Analysis
Technical Summary
The vulnerability in io.netty:netty-codec-http2 involves the HTTP/2-to-HTTP/1.x translation components Http2StreamFrameToHttpObjectCodec and InboundHttp2ToHttpAdapter. When an HTTP/2 client sends both the :authority pseudo-header and a literal host header in the same HEADERS frame, the translation layer maps :authority to Host and also copies the literal host header without deduplication or validation. This leads to an HttpRequest object with two Host headers containing conflicting values controlled by an attacker, classified under CWE-444 (Improper Protection of Alternate Path).
Potential Impact
An attacker can supply conflicting Host headers that may cause the server to route requests incorrectly, potentially bypassing intended routing rules or security controls. This could lead to unauthorized access or manipulation of requests. No known exploits are reported in the wild at this time.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, users should monitor vendor communications for updates. No official fix or workaround is currently documented.
Io.netty:netty codec http2: Netty: [codec-http2] Lack of Host Header Deduplication in HTTP/2→HTTP/1.x Translation Leads to Request Routing Bypass (CVE-2026-59900)
Description
Netty's HTTP/2-to-HTTP/1.x translation layer does not properly deduplicate or validate Host headers when both the :authority pseudo-header and a literal host header are present in a single HTTP/2 HEADERS frame. This results in an HttpRequest object containing two Host headers with differing attacker-controlled values, potentially allowing request routing bypass.
CVSS v4.0
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in io.netty:netty-codec-http2 involves the HTTP/2-to-HTTP/1.x translation components Http2StreamFrameToHttpObjectCodec and InboundHttp2ToHttpAdapter. When an HTTP/2 client sends both the :authority pseudo-header and a literal host header in the same HEADERS frame, the translation layer maps :authority to Host and also copies the literal host header without deduplication or validation. This leads to an HttpRequest object with two Host headers containing conflicting values controlled by an attacker, classified under CWE-444 (Improper Protection of Alternate Path).
Potential Impact
An attacker can supply conflicting Host headers that may cause the server to route requests incorrectly, potentially bypassing intended routing rules or security controls. This could lead to unauthorized access or manipulation of requests. No known exploits are reported in the wild at this time.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, users should monitor vendor communications for updates. No official fix or workaround is currently documented.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-c69g-56f8-xwqj
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-59900"]
- Ecosystems
- ["Maven"]
- Database Specific Severity
- MODERATE
- Cvss Version
- 4.0
Threat ID: 6a6150d39c2644c7f8da06de
Added to database: 07/22/2026, 23:22:59 UTC
Last enriched: 07/22/2026, 23:30:00 UTC
Last updated: 07/22/2026, 23:30:00 UTC
Views: 2
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