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CVE-2026-100659

Netty 4.2.0 through 4.2.17 HTTP/3 Request Routing Bypass

6.9 Medium

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

0.24%Unchanged since Sep 27, 2026
90%50%10%1%

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 MediumCVSS: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 MediumCVSS: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 MediumCVSS: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 MediumCVSS: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 MediumCVSS: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 MediumCVSS: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 MediumCVSS: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 MediumCVSS: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 MediumCVSS: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 MediumCVSS: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

Affected packages
PackageAffectedFixed
netty
Ubuntu: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
netty
Ubuntu: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 less
1:4.0.34-1ubuntu0.1~esm21:4.0.34-1ubuntu0.1~esm31:4.0.34-1ubuntu0.1~esm41:4.0.34-1ubuntu0.1~esm5
None known
netty
Ubuntu: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 less
1:4.1.7-4ubuntu0.1+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
netty
Ubuntu: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 less
1:4.1.45-1ubuntu0.1~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
netty
Ubuntu: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 less
1:4.1.48-4+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
netty
Ubuntu: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 less
1:4.1.48-9ubuntu0.11:4.1.48-9ubuntu0.1+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
netty
Ubuntu:26.10
All versions, plus listed versions
1:4.1.48-161:4.1.48-16ubuntu1
None known
netty
Ubuntu: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

History
RecordedChangedSources
first indexedCVE 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

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