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Advisory record · GHSA-5w3j-gwgh-4rfv

H2O affected by a deserialization vulnerability

CVSS 9.8 CriticalCriticalEPSS 0.0095 · 61st percentile

Critical, because:

  • CVSS score 9.8: 9.0 or more.

How we decide what’s critical

Published by the GitHub Advisory Database at 22 Sept 2025, 18:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
ai.h2o:h2o-coreMaven<=3.46.0.7No fixed version yet
h2oPyPI<=3.46.0.7No fixed version yet
Identifiers
GHSA-5w3j-gwgh-4rfv · CVE-2025-6544 · PYSEC-2026-349
Weakness (CWE)
CWE-502
Tags
Published
22 Sept 2025
Updated
27 Oct 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The H2O package for Maven (ai.h2o:h2o-core) and PyPI (h2o) is vulnerable in versions up to and including 3.46.0.7, due to a deserialization flaw in how JDBC connection parameters are handled. The source says an attacker can bypass regular expression checks using double URL encoding, which can allow reading arbitrary system files and executing arbitrary code. No fixed version is listed, so the source gives no upgrade path; check the advisory for any mitigation guidance.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.8 Critical 3.0 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CNA (@huntr_ai)
  • CISA KEV Not listed.
  • EPSS 0.0095, the 61st percentile, on 13 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:07 UTC First seen by agentprime
  2. 31 Oct 2026, 14:07 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.