Denial of Service Vulnerability in webtransport-go by quic-go
CVE-2026-21435

5.3MEDIUM

Key Information:

Vendor

Quic-go

Status
Webtransport-go
Vendor
CVE Published:
12 February 2026

What is CVE-2026-21435?

The webtransport-go library, which implements the WebTransport protocol, is susceptible to a denial of service condition. Attackers can exploit this vulnerability by preventing or significantly delaying the closure of WebTransport sessions. Specifically, a malicious peer can withhold QUIC flow control credit on the CONNECT stream, disrupting the transmission of the WT_CLOSE_SESSION capsule and causing the closure operation to hang indefinitely. This issue has been addressed in version 0.10.0, making it essential for users to update to this version to mitigate the risk.

Affected Version(s)

webtransport-go < 0.10.0

References

https://github.com/quic-go/webtransport-go/security/advis...
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https://github.com/quic-go/webtransport-go/releases/tag/v...
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CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.