CVE-2026-100659
Netty 4.2.0 through 4.2.17 HTTP/3 Request Routing Bypass
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
6.9
Netty 4.2.0 through 4.2.17 HTTP/3 Request Routing Bypass
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.
- Record
CVE-2026-100659- CVSS 4.0
- 6.9 Medium
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 - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-444
- Updated
- 2026-11-02
EUVDEUVD-2026-87753
6.9
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.
- Record
EUVD-2026-87753- CVSS 4.0
- 6.9 Medium
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 - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-7j27-hw46-m8m8
6.9
Netty's HTTP/3 codec (io.netty:netty-codec-http3) in versions 4.2.0.Final through 4.2.17.Final...
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.
- Record
GHSA-7j27-hw46-m8m8- CVSS 4.0
- 6.9 Medium
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-444
- Updated
- 2026-11-02
NVD
6.9
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.
- Record
CVE-2026-100659- CVSS 4.0
- 6.9 Medium
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-444
- Updated
- 2026-11-02
OSV
6.9
Netty 4.2.0 through 4.2.17 HTTP/3 Request Routing Bypass
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.
- Record
CVE-2026-100659- CVSS 4.0
- 6.9 Medium
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 - Weakness
- CWE-444
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-100659
6.9
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.
- Record
UBUNTU-CVE-2026-100659- CVSS 4.0
- 6.9 Medium
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 - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
nettyUbuntu:Pro:14.04:LTS |
All versions, plus listed versions 1:3.2.6.Final-21:3.2.6.Final-2+deb8u2build0.14.04.1~esm11:3.2.6.Final-2+deb8u2ubuntu0.1~esm1 |
None known |
nettyUbuntu:Pro:16.04:LTS |
All versions, plus listed versions 1:3.2.6.Final-21:4.0.32-11:4.0.33-11:4.0.34-11:4.0.34-1ubuntu0.1~esm1 Show 4 moreShow less1:4.0.34-1ubuntu0.1~esm21:4.0.34-1ubuntu0.1~esm31:4.0.34-1ubuntu0.1~esm41:4.0.34-1ubuntu0.1~esm5 |
None known |
nettyUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 1:4.1.7-41:4.1.7-4ubuntu0.1~esm11:4.1.7-4ubuntu0.11:4.1.7-4ubuntu0.1+esm11:4.1.7-4ubuntu0.1+esm2 Show 5 moreShow less1:4.1.7-4ubuntu0.1+esm31:4.1.7-4ubuntu0.1+esm41:4.1.7-4ubuntu0.1+esm51:4.1.7-4ubuntu0.1+esm61:4.1.7-4ubuntu0.1+esm7 |
None known |
nettyUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 1:4.1.33-11:4.1.33-21:4.1.33-31:4.1.45-11:4.1.45-1ubuntu0.1~esm1 Show 5 moreShow less1:4.1.45-1ubuntu0.1~esm21:4.1.45-1ubuntu0.1~esm31:4.1.45-1ubuntu0.1~esm41:4.1.45-1ubuntu0.1~esm61:4.1.45-1ubuntu0.1~esm7 |
None known |
nettyUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 1:4.1.48-41:4.1.48-4+deb11u1build0.22.04.11:4.1.48-4+deb11u2build0.22.04.11:4.1.48-4+deb11u2ubuntu0.1~esm11:4.1.48-4+deb11u2ubuntu0.1~esm2 Show 5 moreShow less1:4.1.48-4+deb11u2ubuntu0.11:4.1.48-4+deb11u2ubuntu0.1+esm11:4.1.48-4+deb11u2ubuntu0.1+esm31:4.1.48-4+deb11u2ubuntu0.21:4.1.48-4+deb11u2ubuntu0.2+esm1 |
None known |
nettyUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 1:4.1.48-71:4.1.48-81:4.1.48-91:4.1.48-9ubuntu0.1~esm11:4.1.48-9ubuntu0.1~esm2 Show 6 moreShow less1:4.1.48-9ubuntu0.11:4.1.48-9ubuntu0.1+esm11:4.1.48-9ubuntu0.1+esm31:4.1.48-9ubuntu0.21:4.1.48-9ubuntu0.2+esm11:4.1.48-9ubuntu0.2+esm2 |
None known |
nettyUbuntu:26.10 |
All versions, plus listed versions 1:4.1.48-161:4.1.48-16ubuntu1 |
None known |
nettyUbuntu:Pro:26.04:LTS |
All versions, plus listed versions 1:4.1.48-101:4.1.48-111:4.1.48-121:4.1.48-131:4.1.48-141:4.1.48-161:4.1.48-16ubuntu0.1~esm2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-100659 is a medium vulnerability (CVSS 6.9) in Netty, published September 26, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.24%, the 14th percentile. No source names a fixed version.
References
github.com/netty/netty/security/advisories/GHSA-q9pg-8h3j-8hvm
vulncheck.com/advisories/netty-4.2.0-through-4.2.18-http-3-request-routing-bypass
nvd.nist.gov/vuln/detail/CVE-2026-100659
github.com/advisories/GHSA-7j27-hw46-m8m8
github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100659.json
ubuntu.com/security/CVE-2026-100659
cve.org/CVERecord?id=CVE-2026-100659