CVE-2026-47207: Envoy crashes if multiple unexpected ext_proc responses are packed into one gRPC message

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-26 · updated 2026-10-25
Weakness: CWE-416

Description

Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.34.0 until 1.35.13, 1.36.9, 1.37.5, and 1.38.3, Envoy crashes if an ext_proc server sends a single gRPC message containing multiple, specially crafted ProcessingResponse messages. This can occur when the first response in the batch causes the gRPC stream object to be destroyed, leading to a use-after-free error when Envoy attempts to process subsequent responses in the same gRPC message. This vulnerability is fixed in 1.35.13, 1.36.9, 1.37.5, and 1.38.3.

Affected products

envoyproxy envoy: from 1.34.0 before 1.35.13; from 1.36.0 before 1.36.9; from 1.37.0 before 1.37.5; from 1.38.0 before 1.38.3 — fixed in 1.35.13, 1.36.9, 1.37.5, 1.38.3

How to fix

Upgrade to a fixed version: envoyproxy envoy 1.35.13, 1.36.9, 1.37.5, 1.38.3. Check the vendor advisory for mitigations.

References

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