Vendor
H2o vulnerabilities
Updated . Rebuilt every hour.
Junglewise Threat Intelligence has tracked 9 vulnerabilities in H2o: 0 in the last 7 days and 4 in the last 90 days, 0 of them critical and 0 exploited in the wild. The most recent, CVE-2026-55368, was published on 4 November 2026. 3 vulnerabilities in the last four weeks, up from none in the four before. 1 technology has a page of its own.
- Last 7 days
- 0
- Last 90 days
- 4
- Critical, all time
- 0
- Exploited in the wild
- 0
About H2o
A software vendor that develops the H2O open-source distributed machine learning platform.
H2o technologies
Latest H2o vulnerabilities
- CVE-2026-55368: H2O HTTP server buffer overflow in access-log formatterhighCVSS 8.1
- CVE-2026-55367: h2o HTTP server denial of service in CONNECT-UDP parsinghighCVSS 7.5
- CVE-2026-59993: Picotls null pointer dereference in TLS client handshakemediumCVSS 6.5
- CVE-2026-45271: Picotls ASN.1 decoder stack exhaustionmediumCVSS 5.5EPSS 0.1%
- CVE-2026-44436: h2o Quicly denial of service via Connection ID buffer overflowhighCVSS 7.5
- CVE-2026-44435: H2O Quicly assertion failure in CRYPTO stream handlinghighCVSS 7.5
- CVE-2026-44434: h2o Quicly stateless reset injection in lib/quicly.cmediumCVSS 5.3
- CVE-2026-44433: h2o quicly resource exhaustion in flow control credit managementmediumCVSS 5.3
- CVE-2026-55213: h2o stack overflow in QPACK HTTP/3 processinghighCVSS 7.5
Most severe H2o vulnerabilities
Exploited in the wild first, then by severity and CVSS score.
- CVE-2026-55368: H2O HTTP server buffer overflow in access-log formatterhighCVSS 8.1
- CVE-2026-55367: h2o HTTP server denial of service in CONNECT-UDP parsinghighCVSS 7.5
- CVE-2026-44436: h2o Quicly denial of service via Connection ID buffer overflowhighCVSS 7.5
- CVE-2026-44435: H2O Quicly assertion failure in CRYPTO stream handlinghighCVSS 7.5
- CVE-2026-55213: h2o stack overflow in QPACK HTTP/3 processinghighCVSS 7.5
- CVE-2026-59993: Picotls null pointer dereference in TLS client handshakemediumCVSS 6.5
- CVE-2026-45271: Picotls ASN.1 decoder stack exhaustionmediumCVSS 5.5EPSS 0.1%
- CVE-2026-44434: h2o Quicly stateless reset injection in lib/quicly.cmediumCVSS 5.3
- CVE-2026-44433: h2o quicly resource exhaustion in flow control credit managementmediumCVSS 5.3
Vulnerabilities per week
3 vulnerabilities in the last four weeks, up from none in the four before. The last 13 weeks, by the week each vulnerability was published.
| Week of | Bar | Vulns | Critical |
|---|---|---|---|
| 17 Aug 2026 | 1 | 0 | |
| 24 Aug 2026 | 0 | 0 | |
| 31 Aug 2026 | 0 | 0 | |
| 7 Sep 2026 | 0 | 0 | |
| 14 Sep 2026 | 0 | 0 | |
| 21 Sep 2026 | 0 | 0 | |
| 28 Sep 2026 | 0 | 0 | |
| 5 Oct 2026 | 0 | 0 | |
| 12 Oct 2026 | 0 | 0 | |
| 19 Oct 2026 | 0 | 0 | |
| 26 Oct 2026 | 1 | 0 | |
| 2 Nov 2026 | 2 | 0 | |
| 9 Nov 2026 | 0 | 0 |
Embed a badge
A live badge for a README, a status page or an internal wiki: how many H2o vulnerabilities were published in the last 7 days and how many of them are critical, refreshed hourly.
[](https://junglewise.ai/threats/vendors/h2o)<a href="https://junglewise.ai/threats/vendors/h2o"><img src="https://junglewise.ai/threats/vendors/h2o/badge.svg" alt="H2o vulnerabilities" /></a>How this is built
Junglewise Threat Intelligence collects vulnerabilities from NVD, GitHub Security Advisories, OSV, the CISA Known Exploited Vulnerabilities catalog, FIRST EPSS and vendor advisories, and matches each one to the technologies and vendors it affects. Dates are the date a vulnerability was published, in UTC.
The pages are rebuilt from the database every hour. Frozen weekly and monthly reports never change once published, so they can be cited.
Use this data
The same data is at https://junglewise.ai/threats/vendors/h2o.json, and this page as text at https://junglewise.ai/threats/vendors/h2o.md, for scripts and language models. It is free to reuse under CC BY 4.0 with a link back to this page.
Cite as: Junglewise Threat Intelligence, "H2o vulnerabilities", https://junglewise.ai/threats/vendors/h2o, 12 November 2026.