CVE-2026-21438 webtransport-go affected by a Memory Exhaustion Attack due to Missing Cleanup of Streams Map
An attacker can cause unbounded memory consumption and denial of service by repeatedly creating and closing WebTransport streams in webtransport-go.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-21438?
CVE-2026-21438 is a medium-severity denial of service vulnerability in quic-go webtransport-go, published on 12 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-21438?
3 open source packages ship an affected version, including github.com/quic-go/webtransport-go. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/quic-go/webtransport-go Go | All versions | 0.10.0 |
github.com/quic-go/webtransport-go Go | All versions | 0.10.0 |
github.com/quic-go/webtransport-go Go | All versions | 0.10.0 |
Products include Quic-Go Webtransport-Go.
How do I fix CVE-2026-21438?
Upgrade github.com/quic-go/webtransport-go to 0.10.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-21438 being exploited?
There is no known exploitation of CVE-2026-21438 in the wild and no public exploit code.
Other vulnerabilities in quic-go webtransport-go
Sources
Also known as GHSA-2f2x-8mwp-p2gc, GO-2026-4483, MINI-5cj6-55r7-xgw5, MINI-p475-v953-fhcq.