CVE-2026-100663
Netty HTTP/1 CONNECT authority-form mistranslated to malformed HTTP/3
- State
- Published
- Severity
- 8.7 High
- Published
- Sep 26, 2026
- Updated
- Sep 28, 2026
- Reserved
- Sep 26, 2026
Description
Netty's HTTP/3 codec (io.netty:netty-codec-http3) from 4.2.2.Final through 4.2.17.Final does not special-case HTTP/1 CONNECT authority-form request-targets when converting HTTP/1 messages to HTTP/3 in HttpConversionUtil.toHttp3Headers. The authority-form target (e.g., "CONNECT trusted.example:443") is parsed as a URI, so its host is emitted as :scheme, :path is set to "/", and the HTTP/1 Host header is used as :authority; if no Host header is present the CONNECT target is dropped. In a Netty-based HTTP/1-to-HTTP/3 proxy or gateway, a remote client can send a CONNECT request whose Host header names a different authority than the request-target, producing a malformed HTTP/3 CONNECT whose tunnel :authority is attacker-controlled. This can bypass tunnel allow-lists, egress policy, backend selection, or audit controls that validate the HTTP/1 CONNECT request-target before forwarding over HTTP/3. The issue is fixed in 4.2.18.Final.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N | VulnCheck |
Weaknesses
- CWE-20 Improper Input Validation
Affected Products
| Product | Versions |
|---|---|
nettynetty |
|
References
- GitHub Security Advisory (GHSA-jgph-cgq3-c627)vendor-advisory
- VulnCheck Advisory: Netty HTTP/1 CONNECT authority-form mistranslated to malformed HTTP/3third-party-advisory
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