Webtransport GoApplication · Quic Go
CVE-2026-21438
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedwebtransport-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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIn webtransport-go versions prior to 0.10.0, closed WebTransport streams were not removed from an internal session map, preventing garbage collection of their resources. An attacker can exploit this by repeatedly creating and closing many streams to cause unbounded memory consumption on the server.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Webtransport GoApplication
< 0.10.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Determine the version of the webtransport-go library in your projectReview your dependency management files (such as go.mod) or use Go tooling (e.g., go list -m all) to find the version of the webtransport-go library.Affected if The version is less than 0.10.0.
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Verify the library is handling WebTransport streamsInspect your application's source code to confirm whether the webtransport-go library is imported and used to handle WebTransport connections.Affected if The library is in use and the version is below 0.10.0.
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Monitor for unbounded memory growth (optional)Under controlled test conditions, repeatedly create and close WebTransport streams while monitoring the server's memory usage; if memory consumption grows continuously without release, it may indicate the vulnerability.Affected if Memory usage increases unboundedly during repeated stream creation and closure.
You are affected if your environment uses webtransport-go version lower than 0.10.0 to handle WebTransport streams.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped0.10.0
Upgrade to webtransport-go v0.10.0 or later. If immediate upgrade is not feasible, implement stream creation rate limiting and connection pooling to mitigate memory exhaustion while planning the upgrade.
v0.10.0 or later
- Check the current version of webtransport-go in use (e.g., run `go list -m all` or check go.mod)
- Upgrade to version 0.10.0 or later by running `go get github.com/nhooyr.io/[email protected]` or later
- Verify the upgrade was successful by running `go list -m all` to confirm the new version
- Rebuild and test the application to ensure compatibility
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Webtransport Go
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-21438 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-21438 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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