TI-2021-19631 Aliases CVE-2021-43825

Use-after-free in Envoy

LOW 34CWE-416Published 2022-02-22 · Updated 2025-04-23

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 · NVD. 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. Sending a locally generated response must stop further processing of request or response data. Envoy tracks the amount of buffered request and response data and aborts the request if the amount of buffered data is over the limit by sending 413 or 500 responses. However when the buffer overflows while response is processed by the filter chain the operation may not be aborted correctly and result in accessing a freed memory block. If this happens Envoy will crash resulting in a denial of service.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00877 59th 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: No
Technical impact: Partial

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

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
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 1.21.1	1.18.6, 1.19.3, 1.20.2, 1.21.1	Patch available	CNA

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

CPE	Versions	Role	Vendor
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 1.21.1	Vulnerable	envoyproxy

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 →

Product	Status	Plan or fix
OpenShift Service Mesh 2.0	Fixed	RHSA-2022:1276
OpenShift Service Mesh 2.1	Fixed	RHSA-2022:1275

Not affected: 2 products

OpenShift Service Mesh 2.0
OpenShift Service Mesh 2.1

Timeline

2026-10-02 Threatist record created from CVE-2021-43825

References

Patch 1

https://github.com/envoyproxy/envoy/commit/148de954ed3585d8b4298b424aa24916d0de6136

Advisory 1

https://github.com/envoyproxy/envoy/security/advisories/GHSA-h69p-g6xg-mhhh

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