CVE-2021-43826

Name: CVE-2021-43826
Creator: NVD / NIST
Published: 2022-02-22T23:15:10.957+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.05%

Last modified Jun 17, 2026

CVE-2021-43826 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 1.05% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

1.05%

59.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-416

Affected Software

Vendor	Product	Versions
Envoyproxy	Envoy	< 1.18.6
Envoyproxy	Envoy	>= 1.19.0, < 1.19.3
Envoyproxy	Envoy	>= 1.20.0, < 1.20.2
Envoyproxy	Envoy	>= 1.21.0, < 1.21.1

References

https://github.com/envoyproxy/envoy/commit/ce0ae309057a216aba031aff81c445c90c6ef145Patch, Third Party Advisory
https://github.com/envoyproxy/envoy/security/advisories/GHSA-cmx3-fvgf-83mfIssue Tracking, Third Party Advisory
https://github.com/envoyproxy/envoy/commit/ce0ae309057a216aba031aff81c445c90c6ef145Patch, Third Party Advisory
https://github.com/envoyproxy/envoy/security/advisories/GHSA-cmx3-fvgf-83mfIssue Tracking, Third Party Advisory

Timeline

Published: Feb 22, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43826?

How severe is CVE-2021-43826?

CVE-2021-43826 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.05% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43826?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-43826?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST