CVE-2026-44452

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 84% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
5.9
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.9Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
5.9
EG Score
5.9(medium)
EPSS
16.4%
KEV
Not listed

Published

July 16, 2026

Last Modified

July 17, 2026

Advisory Details (1)

Auto-updated Jul 16, 2026
Patch available. Sources: github.
github Patch Available

heap overrun · Advisory · h2o/h2o · GitHub

https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvq

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 10× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:31 UTCEPSS rescore
  5. 2026-07-19 02:32 UTCEG score recompute
  6. 2026-07-19 02:29 UTCEPSS rescore
  7. 2026-07-18 10:04 UTCEPSS rescore
  8. 2026-07-17 14:12 UTCEG score recompute
  9. 2026-07-16 23:43 UTCEG score recompute
  10. 2026-07-16 23:43 UTCNVD updatefirst tracked

Frequently asked(5)

What is CVE-2026-44452?
CVE-2026-44452 is a medium vulnerability published on July 16, 2026. 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…
When was CVE-2026-44452 disclosed?
CVE-2026-44452 was first published in the National Vulnerability Database on July 16, 2026, with the most recent update on July 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-44452 actively exploited?
CVE-2026-44452 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 16.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-44452?
CVE-2026-44452 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2026-44452?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-44452, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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