CVE-2026-21435: GO-2026-4488 - webtransport-go: CloseWithError can block indefinitely in github.com/quic-go/webtransport-go

CVE-2026-21435 · Severity: low · CVSS 3.1 · Published 2026-02-17

webtransport-go: CloseWithError can block indefinitely in github.com/quic-go/webtransport-go

Technologies: github.com/quic-go/webtransport-go (Go). Vendors: Go.

Quick answers

Is CVE-2026-21435 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-21435 being exploited in the wild.
How severe is CVE-2026-21435?
Low severity, with a CVSS score of 3.1, published 17 February 2026.
Which products and versions are affected?
github.com/quic-go/webtransport-go (Go) SEMVER:introduced=0,fixed=0.10.0.
Is there a fix for CVE-2026-21435?
Yes. github.com/quic-go/webtransport-go (Go): upgrade to 0.10.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-21435?
Check whether you run github.com/quic-go/webtransport-go (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/quic-go/webtransport-go (Go): upgrade to 0.10.0 or later
    go get github.com/quic-go/webtransport-go@v0.10.0

Affected products

  • github.com/quic-go/webtransport-go (Go) SEMVER:introduced=0,fixed=0.10.0

Identifiers

  • CVE-2026-21435
  • GHSA-px4r-g4p3-hhqv
  • GO-2026-4488

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