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TI-2021-19632 Aliases CVE-2021-43826

Crash when tunneling TCP over HTTP in Envoy

Priority MEDIUM 41CWE-416Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.01062 64th percentileScored 2026-11-07
Fix Fixed envoy (envoyproxy): 1.18.6, 1.19.3, 1.20.2 +1Red Hat: 2 advisories

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
envoyproxyenvoybefore 1.18.6; 1.19.0 to before 1.19.3; 1.20.0 to before 1.20.2; 1.21.0 to before 1.21.11.18.6, 1.19.3, 1.20.2, 1.21.1Patch availableCNA
  • envoy Vendorenvoyproxy Affected before 1.18.6; 1.19.0 to before 1.19.3; 1.20.0 to before 1.20.2; 1.21.0 to before 1.21.1 Fixed in 1.18.6, 1.19.3, 1.20.2, 1.21.1 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*before 1.18.6; 1.19.0 to before 1.19.3; 1.20.0 to before 1.20.2; 1.21.0 to before 1.21.1Vulnerableenvoyproxy
  • cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* Versions before 1.18.6; 1.19.0 to before 1.19.3; 1.20.0 to before 1.20.2; 1.21.0 to before 1.21.1 Vulnerable ·envoyproxy

Remediation

  • Fix · CNA envoy (envoyproxy) Fixed in 1.18.6, 1.19.3, 1.20.2, 1.21.1

Red Hat 2 advisories

  • RHSA-2022:1275 Released 2022-04-07 · Red Hat rating Important
    Red Hat OpenShift Service Mesh 2.1.2 security update
    • OpenShift Service Mesh 2.1 servicemesh-2.1.2-4.el8, servicemesh-cni-2.1.2-4.el8, servicemesh-pilot-agent-2.1.2-4.el8 +3
  • RHSA-2022:1276 Released 2022-04-07 · Red Hat rating Important
    Red Hat OpenShift Service Mesh 2.0.9 security update
    • OpenShift Service Mesh 2.0 kiali-v1.24.7.redhat1-1.el8, servicemesh-2.0.9-3.el8, servicemesh-istioctl-2.0.9-3.el8 +6

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
OpenShift Service Mesh 2.0Fixed RHSA-2022:1276
OpenShift Service Mesh 2.1Fixed RHSA-2022:1275
Not affected: 2 products
  • OpenShift Service Mesh 2.0
  • OpenShift Service Mesh 2.1

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-43826

References

Patch 1

Advisory 1

  • TI-2026-79288 Out-of-bounds write in Google Brotli decoder KEVCVSS 4.0CRITICAL 9.2
  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2024-20001 HTTP/2: CPU exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
  • TI-2024-18524 HTTP/2: memory exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
  • TI-2023-12215 Envoy client may fake the header `x-envoy-original-path` CVSS 3.1CRITICAL 9.1
  • TI-2023-18002 Envoy vulnerable to OAuth2 credentials exploit with permanent validity CVSS 3.1CRITICAL 9.8
See all 126 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences