How severe is GHSA-g6x7-jq8p-6q9q?

GHSA-g6x7-jq8p-6q9q has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-g6x7-jq8p-6q9q?

GHSA-g6x7-jq8p-6q9q affects the following packages: github.com/quic-go/webtransport-go (Go). Ecosystems affected: Go.

How do I fix GHSA-g6x7-jq8p-6q9q?

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-g6x7-jq8p-6q9q is resolved across your whole dependency graph.

How do I detect GHSA-g6x7-jq8p-6q9q in my Go dependencies?

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.

How do I mitigate GHSA-g6x7-jq8p-6q9q if there is no patch (or I can't update yet)?

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 does O3 Security protect against GHSA-g6x7-jq8p-6q9q?

O3 pinpoints whether GHSA-g6x7-jq8p-6q9q is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-g6x7-jq8p-6q9q actively exploited in the wild?

No public exploit code has been indexed for GHSA-g6x7-jq8p-6q9q yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-g6x7-jq8p-6q9q?

GHSA-g6x7-jq8p-6q9q has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 33th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-g6x7-jq8p-6q9q?

GHSA-g6x7-jq8p-6q9q is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-g6x7-jq8p-6q9q published, and has it been updated?

GHSA-g6x7-jq8p-6q9q was published on February 12, 2026 and was last updated on February 23, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-g6x7-jq8p-6q9q

MEDIUM

webtransport-go: Memory Exhaustion Attack due to Missing Length Check in WT_CLOSE_SESSION Capsule

Also known asCVE-2026-21434GO-2026-4485

Published

Feb 12, 2026

Updated

Feb 23, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk33th percentile+0.39%

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

1 pkg affected

🐹github.com/quic-go/webtransport-go

Real-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 excessive memory consumption in webtransport-go's session implementation by sending a WT_CLOSE_SESSION capsule containing an excessively large Application Error Message. The implementation does not enforce the draft-mandated limit of 1024 bytes on this field, allowing a peer to send an arbitrarily large message payload that is fully read and stored in memory.

This allows an attacker to consume an arbitrary amount of memory. The attacker must transmit the full payload to achieve the memory consumption, but the lack of any upper bound makes large-scale attacks feasible given sufficient bandwidth.

Details

WebTransport over HTTP/3, as defined in draft-ietf-webtrans-http3, uses the WT_CLOSE_SESSION capsule to signal session termination with an optional detailed error. The draft specifies that the length of the Application Error Message in this capsule MUST NOT exceed 1024 bytes. In affected versions of webtransport-go, the parser does not enforce this 1024-byte maximum when processing incoming WT_CLOSE_SESSION capsules. A peer can send a capsule with an excessively large payload, forcing the recipient to allocate and buffer the full amount of transmitted data without bound.

The Fix

webtransport-go now limits the length of the parsed Application Error Message to 1024 bytes in WT_CLOSE_SESSION capsules by reading no more than this amount. This prevents excessive memory consumption.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/quic-go/webtransport-go`	≥ 0.3.0&&< 0.10.0	0.10.0

Detection & mitigation playbook

Open-source dependency

Detect
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-g6x7-jq8p-6q9q 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-g6x7-jq8p-6q9q 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-g6x7-jq8p-6q9q. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Summary An attacker can cause excessive memory consumption in webtransport-go's session implementation by sending a WT_CLOSE_SESSION capsule containing an excessively large Application Error Message. The implementation does not enforce the draft-mandated limit of 1024 bytes on this field, allowing a peer to send an arbitrarily large message payload that is fully read and stored in memory. This allows an attacker to consume an arbitrary amount of memory. The attacker must transmit the full payload to achieve the memory consumption, but the lack of any upper bound makes large-scale attacks f

O3 Security · Impact-Aware SCA

Is GHSA-g6x7-jq8p-6q9q in your dependencies?

O3 detects GHSA-g6x7-jq8p-6q9q across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works