TI-2025-38676 Aliases CVE-2025-62409

Envoy allows large requests and responses to cause TCP connection pool crash

HIGH 68CWE-476Published 2025-10-16 · Updated 2025-10-16

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Partial Red Hat: 2 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-476.

Summary

Envoy is a cloud-native, open source edge and service proxy. Prior to 1.36.1, 1.35.5, 1.34.9, and 1.33.10, large requests and responses can potentially trigger TCP connection pool crashes due to flow control management in Envoy. It will happen when the connection is closing but upstream data is still coming, resulting in a buffer watermark callback nullptr reference. The vulnerability impacts TCP proxy and HTTP 1 & 2 mixed use cases based on ALPN. This vulnerability is fixed in 1.36.1, 1.35.5, 1.34.9, and 1.33.10.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00456 39th percentileScored 2026-11-07

Fix Partial envoy (envoyproxy): 1.36.1, 1.35.5, 1.34.9 +1Red Hat: 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
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

Vendor	Product	Affected versions	Fixed in	Status	Source
envoyproxy	envoy	1.36.0 to before 1.36.1; 1.35.0 to before 1.35.5; 1.34.0 to before 1.34.9; before 1.33.10	1.36.1, 1.35.5, 1.34.9, 1.33.10	Patch available	CNA

envoy Vendorenvoyproxy Affected 1.36.0 to before 1.36.1; 1.35.0 to before 1.35.5; 1.34.0 to before 1.34.9; before 1.33.10 Fixed in 1.36.1, 1.35.5, 1.34.9, 1.33.10 Patch available CNA

CPE configurations NVD · 2

CPE	Versions	Role	Vendor
cpe:2.3:a:envoyproxy:envoy::::::::	before 1.33.11; 1.34.0 to before 1.34.9; 1.35.0 to before 1.35.5	Vulnerable	envoyproxy
cpe:2.3:a:envoyproxy:envoy:1.36.0:::::::*	1.36.0	Vulnerable	envoyproxy

cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* Versions before 1.33.11; 1.34.0 to before 1.34.9; 1.35.0 to before 1.35.5 Vulnerable ·envoyproxy
cpe:2.3:a:envoyproxy:envoy:1.36.0:*:*:*:*:*:*:* Versions 1.36.0 Vulnerable ·envoyproxy

Remediation

Fix · CNA envoy (envoyproxy) Fixed in 1.36.1, 1.35.5, 1.34.9, 1.33.10

Vendor assessments

Red Hat

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

Product	Status	Plan or fix
OpenShift Service Mesh 2	Affected	No fix yet
OpenShift Service Mesh 3	Affected	No fix yet

Not affected: 1 product

OpenShift Service Mesh 3

Timeline

2026-10-02 Threatist record created from CVE-2025-62409

References

Advisory 1

https://github.com/envoyproxy/envoy/security/advisories/GHSA-pq33-4jxh-hgm3

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