Netty's HTTP/3 codec (io.netty:netty-codec-http3) in versions 4.2.0.Final through 4.2.17.Final does not enforce the RFC 9114 requirement that the :authority pseudo-header field and a literal host header field, when both present, carry the same value. A remote unauthenticated peer can send a single HEADERS frame containing both fields with differing, attacker-controlled values; the request is accepted and delivered to the application with two conflicting authorities, allowing routing, virtual-host, and access-control decisions to be bypassed when different components in the request path consult different fields. This issue is fixed in 4.2.18.Final.

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact Low

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Key SSVC decision points have not yet been added.

Affected Vendors & Products

Vendors Products
Netty
  • Netty

No data.

No data.

References
Link Providers
https://github.com/netty/netty/security/advisories/GHSA-q9pg-8h3j-8hvm cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-100659 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-100659 cve-icon
https://www.vulncheck.com/advisories/netty-4.2.0-through-4.2.18-http-3-request-routing-bypass cve-icon cve-icon cve-icon
History

Mon, 28 Sep 2026 19:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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

Sun, 27 Sep 2026 16:45:00 +0000

Type Values Removed Values Added
Title Netty 4.2.0 through 4.2.18 HTTP/3 Request Routing Bypass Netty 4.2.0 through 4.2.17 HTTP/3 Request Routing Bypass

Sun, 27 Sep 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Moderate

Sat, 26 Sep 2026 13:30:00 +0000

Type Values Removed Values Added
Description Netty's HTTP/3 codec (io.netty:netty-codec-http3) in versions 4.2.0.Final through 4.2.17.Final does not enforce the RFC 9114 requirement that the :authority pseudo-header field and a literal host header field, when both present, carry the same value. A remote unauthenticated peer can send a single HEADERS frame containing both fields with differing, attacker-controlled values; the request is accepted and delivered to the application with two conflicting authorities, allowing routing, virtual-host, and access-control decisions to be bypassed when different components in the request path consult different fields. This issue is fixed in 4.2.18.Final.
Title Netty 4.2.0 through 4.2.18 HTTP/3 Request Routing Bypass
First Time appeared Netty
Netty netty
Weaknesses CWE-444
CPEs cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*
Vendors & Products Netty
Netty netty
References
Metrics cvssV3_1

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

cvssV4_0

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

Status: PUBLISHED

Assigner: VulnCheck

Published: 2026-09-26T13:23:26.859Z

Updated: 2026-09-28T18:17:29.170Z

Reserved: 2026-09-26T02:33:59.039Z

Link: CVE-2026-100659

cve-icon Vulnrichment

Updated: 2026-09-28T18:17:03.491Z

cve-icon NVD

Status : Deferred

Published: 2026-09-26T14:16:48.830

Modified: 2026-09-28T19:16:45.480

Link: CVE-2026-100659

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-26T13:23:26Z

Links: CVE-2026-100659 - Bugzilla