CVE-2026-44453

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 59% 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
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: 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 6b5370d, h2o is vulnerable to a Denial of Service attack when calling alloca under certain conditions. When serving static files, h2o builds the file path on stack, by calling alloca. The maximum size of the memory allocated using alloca can be as huge as ~600KB, which exceeds the default pthread stack size used by musl libc (128KB). If the amount of memory allocated by alloca exceeds the stack size, the h2o server crashes with a segmentation fault, while it tries to touch the guard page. This issue has been fixed by commit 6b5370d.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
41%
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

musl libc stack overflow · Advisory · h2o/h2o · GitHub

https://github.com/h2o/h2o/security/advisories/GHSA-rf9v-m59p-mq84

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 9× 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 102 total refreshes for this CVE.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 04:37 UTCEG score recompute
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  1. 2026-08-30 01:22 UTCEPSS rescore
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  74. 2026-07-18 10:04 UTCEPSS rescore
  75. 2026-07-17 14:51 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-44453?
CVE-2026-44453 is a high 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 6b5370d, h2o is vulnerable to a Denial of Service attack when calling alloca under certain conditions. When serving static files, h2o builds the file path on stack, by calling alloca. The maximum size of the memory…
When was CVE-2026-44453 disclosed?
CVE-2026-44453 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-2026-44453 actively exploited?
CVE-2026-44453 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 58.9% of all scored CVEs.
What is the CVSS score of CVE-2026-44453?
CVE-2026-44453 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-44453?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-44453, 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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