CVE-2025-61684 HIGH

CVE-2025-61684: Quicly has assertion failures

Vendor H2O
Product quicly
Weakness CWE-20 · Input validation
Published January 19, 2026
Last update January 20, 2026

CVSS base score

7.5/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality None
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

What the vulnerability does

01Description

Quicly, an IETF QUIC protocol implementation, is susceptible to a denial-of-service attack prior to commit d9d3df6a8530a102b57d840e39b0311ce5c9e14e. A remote attacker can exploit these bugs to trigger an assertion failure that crashes process using Quicly. Commit d9d3df6a8530a102b57d840e39b0311ce5c9e14e fixes the issue.

Key dates

02Disclosure timeline

January 19, 2026 CVE published
January 20, 2026 Record updated