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TI-2026-32392 Aliases CVE-2026-44452

h2o is vulnerable to heap overrun

Priority LOW 27CWE-125Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-125 and the CVSS impact.

Summary

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 8dc37cb, when h2o receives a ClientHello message over TLS or QUIC and it contains a zero-length SNI extension, the h2o server runs over the zero-length hostname while trying to copy the hostname, assuming that it is NULL-terminated. This is a potential denial-of-service attack vector in sense that it might trigger segmentation violation. This issue has been fixed by commit 8dc37cb.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00412 35th percentileScored 2026-11-07
Fix Fixed h2o (h2o): 8dc37cb

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
h2oaih2obefore 8dc37cb8dc37cbPatch availableCNA
  • h2o Vendorh2oai Affected before 8dc37cb Fixed in 8dc37cb Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:h2o:h2o:*:*:*:*:*:*:*:*before 2026-05-29Vulnerableh2oai
  • cpe:2.3:a:h2o:h2o:*:*:*:*:*:*:*:* Versions before 2026-05-29 Vulnerable ·h2oai

Remediation

  • Fix · CNA h2o (h2o) Fixed in 8dc37cb

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-44452

References

Patch 1

Advisory 1

  • TI-2025-05944 Deserialization Vulnerability in h2oai/h2o-3 CVSS 3.0CRITICAL 9.8
  • TI-2024-09776 Jdbc Deserialization in h2oai/h2o-3 CVSS 3.0CRITICAL 9.8
  • TI-2024-30727 H2O.ai H2O through 3.46.0.4 allows attackers to arbitrarily set the JDBC URL, leading to… CVSS 3.1CRITICAL 9.1
  • TI-2026-03424 Remote Code Execution in h2oai/h2o-3 CVSS 3.1CRITICAL 9.8
  • TI-2024-07992 Arbitrary File Overwrite in h2oai/h2o-3 CVSS 3.0HIGH 8.2
  • TI-2023-06020 External Control of File Name or Path in h2oai/h2o-3 CVSS 3.1HIGH 8.2
See all 29 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences