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CVE-2021-43826

Crash when tunneling TCP over HTTP in Envoy

7.5 HighFix available

Envoy is an open source edge and service proxy, designed for cloud-native applications. In affected versions of Envoy a crash occurs when configured for :ref:upstream tunneling <envoy_v3_api_field_extensions.filters.network.tcp_proxy.v3.TcpProxy.tunneling_config> and the downstream connection disconnects while the the upstream connection or http/2 stream is still being established. There are no workarounds for this issue. Users are advised to upgrade.

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
None
Integrity
None
Availability
High

Exploit likelihood

1.06%Up 0.2 points since Feb 23, 2022
90%50%10%1%

What each source reports

CVE List Score used 7.5

Crash when tunneling TCP over HTTP in Envoy

Envoy is an open source edge and service proxy, designed for cloud-native applications. In affected versions of Envoy a crash occurs when configured for :ref:upstream tunneling <envoy_v3_api_field_extensions.filters.network.tcp_proxy.v3.TcpProxy.tunneling_config> and the downstream connection disconnects while the the upstream connection or http/2 stream is still being established. There are no workarounds for this issue. Users are advised to upgrade.

Record
CVE-2021-43826
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-416
Updated
2026-11-02
EUVDEUVD-2021-30706 7.5

Envoy is an open source edge and service proxy, designed for cloud-native applications. In affected versions of Envoy a crash occurs when configured for :ref:upstream tunneling <envoy_v3_api_field_extensions.filters.network.tcp_proxy.v3.TcpProxy.tunneling_config> and the downstream connection disconnects while the the upstream connection or http/2 stream is still being established. There are no workarounds for this issue. Users are advised to upgrade.

Record
EUVD-2021-30706
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
NVD 7.5

Envoy is an open source edge and service proxy, designed for cloud-native applications. In affected versions of Envoy a crash occurs when configured for :ref:upstream tunneling <envoy_v3_api_field_extensions.filters.network.tcp_proxy.v3.TcpProxy.tunneling_config> and the downstream connection disconnects while the the upstream connection or http/2 stream is still being established. There are no workarounds for this issue. Users are advised to upgrade.

Record
CVE-2021-43826
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
4.3 MediumAV:N/AC:M/Au:N/C:N/I:N/A:P
Weakness
CWE-416
Updated
2026-11-02
OSV 7.5

Envoy is an open source edge and service proxy, designed for cloud-native applications. In affected versions of Envoy a crash occurs when configured for :ref:upstream tunneling <envoy_v3_api_field_extensions.filters.network.tcp_proxy.v3.TcpProxy.tunneling_config> and the downstream connection disconnects while the the upstream connection or http/2 stream is still being established. There are no workarounds for this issue. Users are advised to upgrade.

Record
CVE-2021-43826
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVRHSA-2022:1275 9.4

Red Hat Security Advisory: Red Hat OpenShift Service Mesh 2.1.2 security update

Record
RHSA-2022:1275
CVSS 3.1
9.4 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Updated
2026-11-02
OSVRHSA-2022:1276 9.4

Red Hat Security Advisory: Red Hat OpenShift Service Mesh 2.0.9 security update

Record
RHSA-2022:1276
CVSS 3.1
9.4 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Updated
2026-11-02
OSVBIT-envoy-2021-43826 No score

Crash when tunneling TCP over HTTP in Envoy

Envoy is an open source edge and service proxy, designed for cloud-native applications. In affected versions of Envoy a crash occurs when configured for :ref:upstream tunneling <envoy_v3_api_field_extensions.filters.network.tcp_proxy.v3.TcpProxy.tunneling_config> and the downstream connection disconnects while the the upstream connection or http/2 stream is still being established. There are no workarounds for this issue. Users are advised to upgrade.

Record
BIT-envoy-2021-43826
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
envoy
Bitnami
 before 1.18.6, 1.19.0 up to 1.19.3, 1.20.0 up to 1.20.2, 1.21.0 up to 1.21.1
1.18.61.19.31.20.21.21.1
servicemesh-proxy
Red Hat:service_mesh:2.1::el8
From an advisory covering 8 CVEs
 before 0:2.1.2-4.el8
0:2.1.2-4.el8
servicemesh-proxy-debuginfo
Red Hat:service_mesh:2.1::el8
From an advisory covering 8 CVEs
 before 0:2.1.2-4.el8
0:2.1.2-4.el8
servicemesh-proxy-debugsource
Red Hat:service_mesh:2.1::el8
From an advisory covering 8 CVEs
 before 0:2.1.2-4.el8
0:2.1.2-4.el8
servicemesh-proxy-wasm
Red Hat:service_mesh:2.1::el8
From an advisory covering 8 CVEs
 before 0:2.1.2-4.el8
0:2.1.2-4.el8
servicemesh
Red Hat:service_mesh:2.1::el8
From an advisory covering 8 CVEs
 before 0:2.1.2-4.el8
0:2.1.2-4.el8
servicemesh-cni
Red Hat:service_mesh:2.1::el8
From an advisory covering 8 CVEs
 before 0:2.1.2-4.el8
0:2.1.2-4.el8
servicemesh-pilot-agent
Red Hat:service_mesh:2.1::el8
From an advisory covering 8 CVEs
 before 0:2.1.2-4.el8
0:2.1.2-4.el8
servicemesh-pilot-discovery
Red Hat:service_mesh:2.1::el8
From an advisory covering 8 CVEs
 before 0:2.1.2-4.el8
0:2.1.2-4.el8
servicemesh
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:2.0.9-3.el8
0:2.0.9-3.el8
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Affected packages
PackageAffectedFixed
servicemesh-istioctl
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:2.0.9-3.el8
0:2.0.9-3.el8
servicemesh-mixc
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:2.0.9-3.el8
0:2.0.9-3.el8
servicemesh-mixs
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:2.0.9-3.el8
0:2.0.9-3.el8
servicemesh-pilot-agent
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:2.0.9-3.el8
0:2.0.9-3.el8
servicemesh-pilot-discovery
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:2.0.9-3.el8
0:2.0.9-3.el8
kiali
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:v1.24.7.redhat1-1.el8
0:v1.24.7.redhat1-1.el8
servicemesh-prometheus
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:2.14.0-16.el8.1
0:2.14.0-16.el8.1
servicemesh-proxy
Red Hat:service_mesh:2.0::el8
From an advisory covering 16 CVEs
 before 0:2.0.9-3.el8
0:2.0.9-3.el8

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-43826 is a high vulnerability (CVSS 7.5) in Envoyproxy Envoy, published February 22, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.06%, the 64th percentile. Fixed in envoy 1.18.6.

References

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