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.

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploitation poc

Automatable yes

Technical Impact partial

Affected Vendors & Products

Vendors Products
Envoyproxy
  • Envoy

No data.

No data.

References
Link Providers
https://github.com/envoyproxy/envoy/security/advisories/GHSA-pq33-4jxh-hgm3 cve-icon cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2025-62409 cve-icon
https://www.cve.org/CVERecord?id=CVE-2025-62409 cve-icon
History

Tue, 21 Oct 2025 00:30:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

threat_severity

Moderate

Mon, 20 Oct 2025 13:30:00 +0000

Type Values Removed Values Added
First Time appeared Envoyproxy
Envoyproxy envoy
Vendors & Products Envoyproxy
Envoyproxy envoy

Thu, 16 Oct 2025 20:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Thu, 16 Oct 2025 18:00:00 +0000

Type Values Removed Values Added
Description 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.
Title Envoy allows large requests and responses to cause TCP connection pool crash
Weaknesses CWE-476
References
Metrics cvssV4_0

{'score': 6.6, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U'}
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2025-10-16T17:47:25.585Z

Updated: 2025-10-16T19:22:45.332Z

Reserved: 2025-10-13T16:26:12.178Z

Link: CVE-2025-62409

cve-icon Vulnrichment

Updated: 2025-10-16T18:27:19.068Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-10-16T18:15:39.583

Modified: 2025-10-21T19:31:50.020

Link: CVE-2025-62409

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-10-16T17:47:25Z

Links: CVE-2025-62409 - Bugzilla