# H2o Quicly vulnerabilities

Source: https://junglewise.ai/threats/technologies/quicly  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Updated: 9 November 2026, 03:07 UTC. Rebuilt every hour.  
Data: https://junglewise.ai/threats/technologies/quicly.json  
License: CC BY 4.0 with a link back

Junglewise Threat Intelligence has tracked 4 vulnerabilities in H2o Quicly: 0 in the last 7 days and 0 in the last 90 days, 0 of them critical and 0 exploited in the wild. The most recent, CVE-2026-44436, was published on 16 July 2026.

## Counts

- Last 7 days: 0
- Last 30 days: 0
- Last 90 days: 0
- All time: 4 (0 critical, 0 exploited in the wild)

## About H2o Quicly

Quicly is an implementation of the QUIC transport protocol written in C.

## Latest H2o Quicly vulnerabilities

- [CVE-2026-44436: h2o Quicly denial of service via Connection ID buffer overflow](https://junglewise.ai/threats/cve-2026-44436-h2o-quicly-denial-of-service-via-connection-id-buffer-overflow) (high, CVSS 7.5, published 16 Jul 2026)
- [CVE-2026-44435: H2O Quicly assertion failure in CRYPTO stream handling](https://junglewise.ai/threats/cve-2026-44435-h2o-quicly-assertion-failure-in-crypto-stream-handling) (high, CVSS 7.5, published 16 Jul 2026)
- [CVE-2026-44434: h2o Quicly stateless reset injection in lib/quicly.c](https://junglewise.ai/threats/cve-2026-44434-h2o-quicly-stateless-reset-injection-in-lib-quicly-c) (medium, CVSS 5.3, published 16 Jul 2026)
- [CVE-2026-44433: h2o quicly resource exhaustion in flow control credit management](https://junglewise.ai/threats/cve-2026-44433-h2o-quicly-resource-exhaustion-in-flow-control-credit-management) (medium, CVSS 5.3, published 16 Jul 2026)

## Most severe H2o Quicly vulnerabilities

- [CVE-2026-44436: h2o Quicly denial of service via Connection ID buffer overflow](https://junglewise.ai/threats/cve-2026-44436-h2o-quicly-denial-of-service-via-connection-id-buffer-overflow) (high, CVSS 7.5, published 16 Jul 2026)
- [CVE-2026-44435: H2O Quicly assertion failure in CRYPTO stream handling](https://junglewise.ai/threats/cve-2026-44435-h2o-quicly-assertion-failure-in-crypto-stream-handling) (high, CVSS 7.5, published 16 Jul 2026)
- [CVE-2026-44434: h2o Quicly stateless reset injection in lib/quicly.c](https://junglewise.ai/threats/cve-2026-44434-h2o-quicly-stateless-reset-injection-in-lib-quicly-c) (medium, CVSS 5.3, published 16 Jul 2026)
- [CVE-2026-44433: h2o quicly resource exhaustion in flow control credit management](https://junglewise.ai/threats/cve-2026-44433-h2o-quicly-resource-exhaustion-in-flow-control-credit-management) (medium, CVSS 5.3, published 16 Jul 2026)

## Vulnerabilities per week

Nothing was published in the last eight weeks.

| Week of | Vulns | Critical | Exploited |
| --- | --- | --- | --- |
| 17 Aug 2026 | 0 | 0 | 0 |
| 24 Aug 2026 | 0 | 0 | 0 |
| 31 Aug 2026 | 0 | 0 | 0 |
| 7 Sep 2026 | 0 | 0 | 0 |
| 14 Sep 2026 | 0 | 0 | 0 |
| 21 Sep 2026 | 0 | 0 | 0 |
| 28 Sep 2026 | 0 | 0 | 0 |
| 5 Oct 2026 | 0 | 0 | 0 |
| 12 Oct 2026 | 0 | 0 | 0 |
| 19 Oct 2026 | 0 | 0 | 0 |
| 26 Oct 2026 | 0 | 0 | 0 |
| 2 Nov 2026 | 0 | 0 | 0 |
| 9 Nov 2026 | 0 | 0 | 0 |

## Sources

NVD, GitHub Security Advisories, OSV, the CISA Known Exploited Vulnerabilities catalog, FIRST EPSS and vendor advisories. Rebuilt every hour. Cite as: Junglewise Threat Intelligence, "H2o Quicly vulnerabilities", https://junglewise.ai/threats/technologies/quicly, 9 November 2026.