Resource exhaustion in Quic-Go Webtransport-Go
CVE-2026-21435
webtransport-go is an implementation of the WebTransport protocol. Prior to v0.10.0, 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. This vulnerability is fixed in v0.10.0.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.004 (34.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 34.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000
Affected products
- Quic-Go Webtransport-Go — versions < 0.10.0
Weakness classification (CWE)
References
- github.com/quic-go/webtransport-go/security/advisories/GHSA-px4r-g4p3-hhqv (Vendor Advisory)
- github.com/quic-go/webtransport-go/releases/tag/v0.10.0 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-21435?
- CVE-2026-21435 is a medium-severity vulnerability in Quic-Go Webtransport-Go, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-02-12.
- How severe is CVE-2026-21435?
- Medium severity. CVSS v3 base score is 5.3 out of 10.