{"id":"CVE-2026-21435","aliases":["GHSA-px4r-g4p3-hhqv","GO-2026-4488"],"url":"https://o3.security/vulnerability/CVE-2026-21435","summary":"webtransport-go CloseWithError can block indefinitely","details":"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.","published":"2026-02-12T18:22:58.098Z","modified":"2026-08-05T03:32:26.092825762Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/quic-go/webtransport-go","fixedVersion":"0.10.0"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/quic-go/webtransport-go/releases/tag/v0.10.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/21xxx/CVE-2026-21435.json"},{"type":"ADVISORY","url":"https://github.com/quic-go/webtransport-go/security/advisories/GHSA-px4r-g4p3-hhqv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-21435"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-05T03:32:26.092825762Z"}}