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.

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 wit…

Vulnerability class: DoS (Denial of Service)

EPSS: 0.004 (33.0th percentile) — read the EPSS interpretation.

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.

Affected products

Quic-go Webtransport-go — versions < 0.10.0

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
security-advisories@github.com (Product, x_refsource_MISC, 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.