Preface: mvfst (Pronounced move fast) is a client and server implementation of IETF QUIC protocol in C++ by Facebook. QUIC is a UDP based reliable, multiplexed transport protocol that will become an internet standard.

Background: QUIC (Quick UDP Internet Connections), was designed with the primary goal of enhancing the speed and reliability of internet connections, particularly for latency-sensitive and bandwidth-intensive applications. It aims to reduce connection setup time, improve data transfer speeds, and enhance security compared to traditional TCP and TLS protocols.

The QUIC protocol is a key component in modern CDN (Content Delivery Network) strategies, particularly with the rise of HTTP/3. QUIC, developed by Google and standardized by the IETF, is a transport layer protocol that offers significant performance and security improvements over traditional TCP, especially in the context of CDNs.

Vulnerability details: A heap-buffer-overflow vulnerability is possible in mvfst via a specially crafted message during a QUIC session. This issue affects mvfst versions prior to v2025.07.07.00.

Does removing maxBatchSize affect performance?

Yes, potentially.

To offset any performance degradation from removing maxBatchSize, CDNs may:

-Optimize packet scheduling and batching elsewhere in the QUIC stack to maintain throughput.

-Use adaptive batching: Dynamically adjust how many packets are processed based on system load and traffic patterns.

-Deploy hardware acceleration: Offload QUIC processing to specialized hardware (e.g., SmartNICs or FPGAs).

-Leverage edge caching: Reduce the need for frequent QUIC connections by serving more content directly from edge nodes.

Official announcement: Please refer to the url  for details – https://nvd.nist.gov/vuln/detail/CVE-2025-30403