CVE-2026-21435
Medium
Description
webtransport-go is an implementation of the WebTransport protocol. Prior to v0.10.0, an attacker can cause a denial of service in webtransport-go by preventing or indefinitely delaying WebTransport session closure. A malicious peer can withhold QUIC flow control credit on the CONNECT stream, blocking transmission of the WT_CLOSE_SESSION capsule and causing the close operation to hang. This vulnerability is fixed in v0.10.0.
SeverityMedium
CVSS5.3
Exploit probability—
ProductQuic-go Webtransport-go
PublishedFeb 12, 2026
First seenFeb 12, 2026
Weakness typeCWE-400Uncontrolled resource consumption
How to fix
Update
- quic-go webtransport-go0.10.0 or later
- github.com/quic-go/webtransport-go0.10.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| quic-go webtransport-go | v < 0.10.0 | 0.10.0 |
| github.com/quic-go/webtransport-goGo | v < 0.10.0 | 0.10.0 |
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