# h2o vulnerabilities & exploitation

> As of 2026-10-05, Threadlinqs tracks 6 h2o CVEs, 0 in the CISA Known Exploited Vulnerabilities catalog, linked to 0 tracked threat campaigns.

**Data as of:** 2026-10-05

## Exploitation timeline

Threadlinqs has recorded 6 h2o CVEs published between 2026-07-15 and 2026-07-15. The busiest month was 2026-07 (6 new CVEs). None of them is listed in CISA KEV yet.

## Most exploited vulnerabilities

Ranked with CISA KEV listings first, then EPSS exploit probability, then CVSS score. Showing 6 of 6 tracked h2o CVEs.

- [CVE-2026-44435](https://intel.threadlinqs.com/cve/CVE-2026-44435) — HIGH 7.5 · EPSS 0.3% · 2026-07-16
- [CVE-2026-44436](https://intel.threadlinqs.com/cve/CVE-2026-44436) — HIGH 7.5 · EPSS 0.3% · 2026-07-16
- [CVE-2026-44452](https://intel.threadlinqs.com/cve/CVE-2026-44452) — MEDIUM 5.9 · EPSS 0.3% · 2026-07-16
- [CVE-2026-44453](https://intel.threadlinqs.com/cve/CVE-2026-44453) — HIGH 7.5 · 2026-07-16
- [CVE-2026-44433](https://intel.threadlinqs.com/cve/CVE-2026-44433) — MEDIUM 5.3 · 2026-07-16
- [CVE-2026-44434](https://intel.threadlinqs.com/cve/CVE-2026-44434) — MEDIUM 5.3 · 2026-07-16

## Products affected

Threadlinqs normalises CPE and CNA product records across all 6 CVEs; 2 distinct h2o products are affected. The most frequently affected:

- quicly — 4 CVEs
- h2o — 2 CVEs

## Threat activity

No tracked threat campaign references h2o products or CVEs yet. Vulnerability records are still monitored for exploitation and linked as campaigns are ingested.

## How to prioritise h2o patching

This order follows the data Threadlinqs holds for h2o, not a generic severity checklist:

- No h2o CVE is in CISA KEV yet, so rank by exploit probability instead.
- Outside KEV, the highest EPSS scores are [CVE-2026-44435](https://intel.threadlinqs.com/cve/CVE-2026-44435) (0.3%), [CVE-2026-44436](https://intel.threadlinqs.com/cve/CVE-2026-44436) (0.3%), [CVE-2026-44452](https://intel.threadlinqs.com/cve/CVE-2026-44452) (0.3%).
- 0 CVEs score Critical and 3 High on CVSS v3 (maximum 7.5, average 6.5); sequence these after KEV and high-EPSS items.

## About this data

Vendor attribution comes from the CNA and CPE product records of each CVE, folded to one vendor name; CVSS, EPSS and KEV status are read from the Threadlinqs CVE catalog; campaign and actor links come from tracked threat records. Counts reflect the data as of 2026-10-05 and refresh daily.

Canonical: https://intel.threadlinqs.com/vendors/h2o
All vendors: https://intel.threadlinqs.com/vendors
Full detection coverage and IOCs via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp