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Response snapshot Oct 27, 2026, 18:26 UTC

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VulnerabilityCVE-2025-6544

H2O affected by a deserialization vulnerability

A deserialization vulnerability exists in h2oai/h2o-3 versions <= 3.46.0.7, allowing attackers to read arbitrary system files and execute arbitrary code.

At a glance

Exploited
Not known
Severity
9.8 Critical (CVSS 3.0)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Consult the exact GitHub advisory for affected versions, mitigation, and patch availability.

Read GitHub-reviewed advisory GHSA-5w3j-gwgh-4rfv (opens a new tab)

What happened

A deserialization vulnerability exists in h2oai/h2o-3 versions <= 3.46.0.7, allowing attackers to read arbitrary system files and execute arbitrary code. The vulnerability arises from improper handling of JDBC connection parameters, which can be exploited by bypassing regular expression checks and using double URL encoding. This issue impacts all users of the affected versions.

Affected package ranges reported by GitHub: ai.h2o:h2o-core: <= 3.46.0.7 h2o: <= 3.46.0.7

Scores and how they were measured

CVSS base severity

9.8

Version 3.0As of

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-5w3j-gwgh-4rfv (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-5w3j-gwgh-4rfv, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 27). H2O affected by a deserialization vulnerability (CVE-2025-6544). https://kevwire.com/record/CVE-2025-6544

MLA

"H2O affected by a deserialization vulnerability (CVE-2025-6544)." KEVWire, 27 Oct. 2026, kevwire.com/record/CVE-2025-6544.

Chicago

KEVWire. "H2O affected by a deserialization vulnerability (CVE-2025-6544)." Last modified October 27, 2026. https://kevwire.com/record/CVE-2025-6544.

Evidence summary (plain text)

H2O affected by a deserialization vulnerability (Sep 22, 2025).
A deserialization vulnerability exists in h2oai/h2o-3 versions <= 3.46.0.7, allowing attackers to read arbitrary system files and execute arbitrary code. The vulnerability arises from improper handling of JDBC connection parameters, which can be exploited by bypassing regular expression checks and using double URL encoding. This issue impacts all users of the affected versions.
CVSS 9.8 (version 3.0; evidence as of Oct 27, 2026; https://github.com/advisories/GHSA-5w3j-gwgh-4rfv).
Sources:
GitHub-reviewed advisory GHSA-5w3j-gwgh-4rfv: https://github.com/advisories/GHSA-5w3j-gwgh-4rfv
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2025-6544.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 18:10 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

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