CVE-2026-100663 (GCVE-0-2026-100663)

Vulnerability from cvelistv5 – Published: 2026-09-26 13:23 – Updated: 2026-09-28 18:48
VLAI
Title
Netty HTTP/1 CONNECT authority-form mistranslated to malformed HTTP/3
Summary
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.
Severity
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
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
SSVC
Exploitation: poc Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-28 18:48 UTC
CWE
  • CWE-20 - Improper Input Validation
Assigner
VulnCheck CNA under the mitre root
CNA scorecard B 84/100 over 8184 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
netty netty Affected: 4.2.2.Final , < 4.2.18.Final (custom)
Unaffected: 4.2.18.Final (custom)
    cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*
Create a notification for this product.
Date Public
2026-09-10 00:00
Credits
rexpository
Show details on NVD website
To clipboard 

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