CVE-2026-21438: Quic-Go Webtransport-Go

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

webtransport-go is an implementation of the WebTransport protocol. Prior to 0.10.0, an attacker can cause unbounded memory consumption repeatedly creating and closing many WebTransport streams. Closed streams were not removed from an internal session map, preventing garbage collection of their resources. This vulnerability is fixed in v0.10.0.

Affected products

• Quic-Go Webtransport-Go: before 0.10.0 (fixed in 0.10.0)

Published 2026-02-12. Last modified 2026-06-17.