Executive brief
Netty is a widely used Java networking library that powers many high-performance applications and services. A memory leak flaw in its HAProxy protocol handler allows an attacker to exhaust available memory by sending malformed protocol messages, causing the affected application to crash or become unresponsive. This denial-of-service attack requires no authentication and can be triggered remotely.
Technical details
The vulnerability is a reference-count leak in Netty's HAProxy PROXY-v2 message decoder. When specially crafted PROXY-protocol v2 headers are received, the decoder fails to properly release memory references, causing them to accumulate over time. An unauthenticated attacker on the network can repeatedly send malformed PROXY-v2 messages to trigger this leak, leading to memory exhaustion and eventual denial of service. The attack is network-accessible and requires no prior authentication or user interaction. A fix is expected in an upstream Netty release.
Affected products
- Netty Netty
Timeline
- 2026-09-18: disclosed