CVE-2025-61684
High
Description
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.
SeverityHigh
CVSS7.5
Exploit probability—
Product
H2o Quicly
PublishedJan 19, 2026
First seenJan 19, 2026
Weakness typeCWE-20Improper input validation
How to fix
Update
- h2o quicly2026-01-18 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| h2o quicly | v < 2026-01-18 | 2026-01-18 |
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