CVE-2026-21435

low-risk
Published 2026-02-12

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.

Do I need to act?

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0.02% chance of exploitation
EPSS score — low exploit probability
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
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Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
5
CVSS 5.3/10 Medium
NETWORK / LOW complexity

Affected Products (1)

Webtransport-Go

Affected Vendors

Quic-Go

References (2)

Product https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0
Vendor Advisory https://github.com/quic-go/webtransport-go/security/advisories/GHSA-px4r-g4p3-hh...
26
/ 100
low-risk
Severity 21/34 · High
Exploitability 0/34 · Minimal
Exposure 5/34 · Minimal