{"cve":"CVE-2026-21435","nvd":{"published":"2026-02-12T19:15:51.503","modified":"2026-06-17T10:18:40.043","status":"Analyzed","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400"],"references":["https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0","https://github.com/quic-go/webtransport-go/security/advisories/GHSA-px4r-g4p3-hhqv"],"products":["quic-go:webtransport-go"],"source":"nvd","synced_at":"2026-10-19T22:23:35.260773158+00:00"},"epss":{"cve":"CVE-2026-21435","score":0.00465,"percentile":0.40277,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-px4r-g4p3-hhqv","url":"https://osv.dev/vulnerability/GHSA-px4r-g4p3-hhqv","summary":"webtransport-go: CloseWithError can block indefinitely","modified":"2026-09-10T03:50:59.526564021Z","packages":[{"ecosystem":"Go","name":"github.com/quic-go/webtransport-go","purl":"pkg:golang/github.com/quic-go/webtransport-go","ranges":["<0.10.0"],"fixed":["0.10.0"]}]},{"id":"GO-2026-4488","url":"https://osv.dev/vulnerability/GO-2026-4488","summary":"webtransport-go: CloseWithError can block indefinitely in github.com/quic-go/webtransport-go","modified":"2026-02-23T12:43:59.680487Z","packages":[{"ecosystem":"Go","name":"github.com/quic-go/webtransport-go","purl":"pkg:golang/github.com/quic-go/webtransport-go","ranges":["<0.10.0"],"fixed":["0.10.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}