What’s Vulnerable › Vulnerabilities

CVE-2026-21438: webtransport-go affected by a Memory Exhaustion Attack due to Missing Cleanup of Streams Map

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-12 · updated 2026-06-17
• Weakness: CWE-401

Description

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

How to fix

Upgrade to a fixed version: quic-go webtransport-go 0.10.0. Check the vendor advisory for mitigations.

References

• https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0
• https://github.com/quic-go/webtransport-go/security/advisories/GHSA-2f2x-8mwp-p2gc

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