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: 0.4%, top 65% 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
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.9Exploit: None knownExposed: 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)
EG Risk
27(Track)
EG Risk 27/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity59% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
35%
KEV
Not listed

Published

July 16, 2026

Last Modified

August 6, 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

Affected Packages

(2 across 2 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
h2o2.2.5+dfsg2-10 ... 2.2.5+dfsg2-9 (10 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
h2o2.2.5+dfsg2-10 ... 2.2.5+dfsg2-9 (7 versions)——

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 40× 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.

Showing the most recent 100 of 103 total refreshes for this CVE.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 09:59 UTCEG score recompute
  3. 2026-09-17 19:31 UTCEPSS rescore
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  1. 2026-08-30 01:22 UTCEPSS rescore
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  27. 2026-08-14 10:59 UTCEG score recompute
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  74. 2026-07-19 02:29 UTCEPSS rescore
  75. 2026-07-18 10:04 UTCEPSS rescore

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 August 6, 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 0% probability of exploitation in the next 30 days, which ranks it in the top 64.8% of all scored CVEs.
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.

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