GHSA-px4r-g4p3-hhqv
MEDIUMwebtransport-go: CloseWithError can block indefinitely
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
github.com/quic-go/webtransport-goReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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.
Details
WebTransport over HTTP/3 signals session termination by sending a WT_CLOSE_SESSION capsule on the CONNECT stream. The capsule is only needed to transmit a reason phrase and an error code to the peer. After the capsule is sent, the CONNECT stream is closed. In affected versions, the closure procedure blocked indefinitely while waiting for sufficient QUIC flow control credit from the peer. A malicious peer can withhold this credit, preventing the capsule from being sent.
The Fix
webtransport-go now attempts to send the WT_CLOSE_SESSION capsule with a short deadline. If the capsule cannot be sent within this deadline, the CONNECT stream is reset instead. This closes the WebTransport session promptly without transmitting the optional error details. This prevents indefinite blocking on session closure.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/quic-go/webtransport-go | all versions | 0.10.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/quic-go/webtransport-go. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/quic-go/webtransport-go to 0.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-px4r-g4p3-hhqv is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-px4r-g4p3-hhqv is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-px4r-g4p3-hhqv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-px4r-g4p3-hhqv in your dependencies?
O3 detects GHSA-px4r-g4p3-hhqv across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.