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OpenAdvisories
High · 7.5 CVE-2026-44435 EUVD-2026-45071

Quicly: Remote Denial of Service via assertion failure when CRYPTO stream handshake data exceeds 32KB

Published Jul 16, 2026 · Updated Jul 17, 2026 · Assigned by GitHub_M

Description

Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 937d0e9, an assertion failure is raised when the total number of valid handshake messages received over a CRYPTO stream of a single packet number space exceeds 32KB, causing a Denial of Service. This issue has been fixed by commit 937d0e9.

Affected products

VendorProductAffectedFixed
h2o quicly < 937d0e9 —

References