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CVE record · CVE-2026-55367

h2o: heap exhaustion using capsules

CVSS 7.5 HighEPSS 0.0034 · 27th percentile

Published by the CVE Program (CNA: GitHub_M) at 4 Nov 2026, 21:39 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
VendorProductVersions
h2o h2o
  • affected < 4212ce114506a073505fd389db16ad2ba4e582a0
Identifiers
CVE-2026-55367
CNA
GitHub_M
Weakness (CWE)
CWE-770
Tags
Published
4 Nov 2026
Updated
5 Nov 2026

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.5 High 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0034, the 27th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 4 Nov 2026, 21:39 UTC Confirmed by the CVE List
  2. 4 Nov 2026, 21:48 UTC First seen by agentprime
  3. 4 Nov 2026, 22:18 UTC Confirmed by NVD

Sources

References from the CNA

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.