Resource exhaustion in H3js H3
CVE-2026-86250
h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie() functions. Attackers can send a crafted cookie header with an extremely large chunk count to trigger an O(n²) cleanup loop that hangs the server process.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (41.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 41st percentile — 41.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/h3js/h3/security/advisories/GHSA-q5pr-72pq-83v3 (vendor-advisory)
- www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-denial-of-service-via-unboun… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-86250?
- CVE-2026-86250 is a high-severity vulnerability in H3js H3, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-09-06.
- How severe is CVE-2026-86250?
- High severity. CVSS v3 base score is 7.5 out of 10.