CVE-2023-50247 : Vulnerability Insights and Analysis

Understanding CVE-2023-50247

This CVE involves the h2o HTTP server with support for HTTP/1.x, HTTP/2, and HTTP/3, where the QUIC stack (quicly) is vulnerable to a state exhaustion denial-of-service (DoS) attack.

What is CVE-2023-50247?

The vulnerability in h2o allows a remote attacker to exploit the QUIC stack used by H2O, leading to a state exhaustion attack. This can result in a progressive increase in memory usage by the QUIC stack, potentially causing H2O to crash due to memory exhaustion.

The Impact of CVE-2023-50247

The impact of this CVE is a denial-of-service (DoS) attack on the h2o HTTP server, specifically affecting HTTP/3 traffic. This vulnerability could be exploited by remote attackers to disrupt services relying on the affected versions of h2o.

Technical Details of CVE-2023-50247

This section provides insights into the vulnerability description, affected systems, and exploitation mechanism.

Vulnerability Description

The vulnerability lies in the QUIC stack (quicly) used by H2O up to version 2.3.0-beta2. A remote attacker targeting HTTP/3 traffic can manipulate the QUIC stack to exhaust system memory progressively, potentially leading to H2O server crashes.

Affected Systems and Versions

The affected system is the h2o HTTP server with versions equal to or below 2.3.0-beta2. Specifically, this vulnerability impacts the usage of HTTP/3 and not HTTP/1 or HTTP/2.

Exploitation Mechanism

Exploiting this vulnerability involves manipulating the QUIC stack during HTTP/3 sessions to exhaust memory resources progressively, eventually causing the server to terminate due to memory depletion.

Mitigation and Prevention

In this section, we discuss immediate steps and long-term security practices to mitigate the risks associated with CVE-2023-50247.

Immediate Steps to Take

To address this vulnerability immediately, administrators can disable HTTP/3 support in the h2o HTTP server. While a permanent fix involves updating to the patched version, disabling the affected protocol can prevent exploitation.

Long-Term Security Practices

Ensuring timely updates and patches for the h2o server is crucial for long-term security. Regularly monitoring security advisories and promptly applying fixes can help prevent future vulnerabilities.

Patching and Updates

The vulnerability has been addressed in commit d67e81d03be12a9d53dc8271af6530f40164cd35. Administrators are advised to upgrade their h2o servers to the patched version to eliminate the risk of state exhaustion DoS attacks.