CVE-2024-45403: H2O assertion failure when HTTP/3 requests are cancelled

Vulnerability summary

CVE-2024-45403 is a high (CVSS 7.5) Reachable Assertion vulnerability in dena h2o. EPSS estimates a 0.65% chance of exploitation in the next 30 days, higher than 51.3% of scored vulnerabilities.

Timeline

1. 11-10-2024
   PublishedVulnerability first disclosed.
2. 11-10-2024
   Last modifiedVulnerability information updated.

Description

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When h2o is configured as a reverse proxy and HTTP/3 requests are cancelled by the client, h2o might crash due to an assertion failure. The crash can be exploited by an attacker to mount a Denial-of-Service attack. By default, the h2o standalone server automatically restarts, minimizing the impact. However, HTTP requests that were served concurrently will still be disrupted. The vulnerability has been addressed in commit 1ed32b2. Users may disable the use of HTTP/3 to mitigate the issue.

• CWE-617Reachable AssertionThe product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.