CVE-2026-8751: A security flaw has been discovered in h2oai h2o-3 up to 7402

Q: How do I fix CVE-2026-8751?

h2o: upgrade to newer than 7402. Exact commands for each OS are on this page.

Q: Is CVE-2026-8751 being exploited?

CVE-2026-8751 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-8751 affect?

CVE-2026-8751 affects h2o. Severity is high (CVSS 7.3). A security flaw has been discovered in h2oai h2o-3 up to 7402. This affects the function importBinaryModel of the file h2o-core/src/main/java/hex/Model.java of the component JAR Handler. Performing a manipulation results in deserialization.

Q: How urgent is CVE-2026-8751?

Priority 39/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.3REMOTEUPGRADE

CVE-2026-8751 is a high-severity flaw (CVSS 7.3) affecting h2o. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A security flaw has been discovered in h2oai h2o-3 up to 7402. This affects the function importBinaryModel of the file h2o-core/src/main/java/hex/Model.java of the component JAR Handler. Performing a manipulation results in deserialization. The attack is possible to be carried out remotely. The exploit has been released to the public and may be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.3 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 65%)
CISA exploited list	No
Weakness	CWE-20, CWE-502
Published	2026-05-17
Last modified	2026-10-14

Publisher (CNA): VulDB · Vendor: h2o

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-17 12:16 UTCPublished CVE record published
2026-10-14 20:10 UTCUpdated Record last modified

h2o h2o UPGRADE

Affected: <= 7402

Fixed in: newer than 7402

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy h2o || rpm -q h2o || h2o --version

2. UPGRADE to newer than 7402 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade h2o

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade h2o

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-8751?

h2o: upgrade to newer than 7402. Exact commands for each OS are on this page.

Is CVE-2026-8751 being exploited?

CVE-2026-8751 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-8751 affect?

CVE-2026-8751 affects h2o. Severity is high (CVSS 7.3). A security flaw has been discovered in h2oai h2o-3 up to 7402. This affects the function importBinaryModel of the file h2o-core/src/main/java/hex/Model.java of the component JAR Handler. Performing a manipulation results in deserialization.

How urgent is CVE-2026-8751?

Priority 39/100. High severity; Remotely exploitable, no login, no user action

Software pages

Java vulnerabilities

Related CVEs

CVE-2026-3960 CRITICAL 9.8 UPGRADE A critical remote code execution vulnerability exists in the unauthenticated REST API endpoint /99/ImportSQLTa
CVE-2026-8750 MEDIUM 5.3 UPGRADE A vulnerability was identified in h2oai h2o-3 up to 7402
CVE-2026-8752 MEDIUM 5.3 UPGRADE A weakness has been identified in h2oai h2o-3 up to 7402
CVE-2026-44452 MEDIUM 5.9 UPGRADE h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3
CVE-2026-44453 HIGH 7.5 UPGRADE h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3

References

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