Vulnerability Description
webtransport-go is an implementation of the WebTransport protocol. From 0.3.0 to 0.9.0, 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. This vulnerability is fixed in 0.10.0.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Quic-Go | Webtransport-Go | >= 0.3.0, < 0.10.0 |
Related Weaknesses (CWE)
References
- https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0ProductRelease Notes
- https://github.com/quic-go/webtransport-go/security/advisories/GHSA-g6x7-jq8p-6qVendor Advisory
FAQ
What is CVE-2026-21434?
CVE-2026-21434 is a vulnerability with a CVSS score of 5.3 (MEDIUM). webtransport-go is an implementation of the WebTransport protocol. From 0.3.0 to 0.9.0, an attacker can cause excessive memory consumption in webtransport-go's session implementation by sending a WT_C...
How severe is CVE-2026-21434?
CVE-2026-21434 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-21434?
Check the references section above for vendor advisories and patch information. Affected products include: Quic-Go Webtransport-Go.