Read the docs
TI-2025-38115 Aliases CVE-2025-61684

Quicly has assertion failures

Priority LOW 39CWE-20Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-617.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00395 33rd percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
h2oaiquicly< d9d3df6—No fix listedCNA
  • quicly Vendorh2oai Affected < d9d3df6 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:h2o:quicly:*:*:*:*:*:*:*:*before 2026-01-18Vulnerableh2oai
  • cpe:2.3:a:h2o:quicly:*:*:*:*:*:*:*:* Versions before 2026-01-18 Vulnerable ·h2oai

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-61684

References

Patch 1

Advisory 1

  • TI-2026-32377 Quicly is vulnerable to connection state corruption CVSS 3.1HIGH 7.5
  • TI-2026-32376 Quicly: Remote Denial of Service via assertion failure when CRYPTO stream handshake data exceeds 32KB CVSS 3.1HIGH 7.5
  • TI-2026-32374 Quicly is vulnerable to memory exhaustion CVSS 3.1HIGH 7.5
  • TI-2026-32375 Quicly is vulnerable to stateless reset injection CVSS 3.1MEDIUM 5.3

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences