Executive brief
Envoy, a widely used service proxy for cloud-native applications, is vulnerable to a denial-of-service attack. By sending a specially crafted, deeply nested JSON message, an attacker can cause the proxy to crash when it attempts to process and then clean up the data. This can lead to service outages and disruptions in network traffic management.
Technical details
A stack overflow vulnerability exists in Envoy's JSON processing logic, specifically within the destructor of JSON objects. While the 'loadFromString' method can successfully parse deeply nested JSON (approximately 100,000 levels), the subsequent destruction of the resulting object graph relies on recursive calls that exhaust the stack. An unauthenticated remote attacker can trigger this by sending a malicious JSON payload to any filter using the affected hot path, such as the McpRouter or JsonToMetadata filter. This results in a segmentation fault and process crash. The issue is fixed in versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1.
Affected products
- Envoy Proxy Envoy >= 1.18, < 1.35.11; >= 1.36.0, < 1.36.7; >= 1.37.0, < 1.37.3; >= 1.38.0, < 1.38.1
Timeline
- 2026-06-23: advisory: GitHub Security Advisory published
- 2026-06-26: disclosed: CVE published to NVD