Critical 10.0Published Mar 20, 2026

CVE-2026-33128H3 is a minimal H(TTP) framework.

Updated under an hour ago (2026-10-19 06:25 UTC)

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It affects h3. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for h3

Exploited in the last 30 days

H3 is a minimal H(TTP) framework. In versions prior to 1.15.6 and between 2.0.0 through 2.0.1-rc.14, createEventStream is vulnerable to Server-Sent Events (SSE) injection due to missing newline sanitization in formatEventStreamMessage() and formatEventStreamComment(). An attacker who controls any part of an SSE message field (id, event, data, or comment) can inject arbitrary SSE events to connected clients. This issue is fixed in versions 1.15.6 and 2.0.1-rc.15.

CVSS: 10.0 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness (CWE): CWE-93
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Not given
NVD analysis: Analyzed
Record last updated: Jun 17, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

h3 h3 h3:h3	before 1.15.6; 2.0.0; 2.0.1; 2.0.1; 2.0.1; 2.0.1; 2.0.1; 2.0.1; and 7 more ranges	NVD

References

https://github.com/h3js/h3/blob/52c82e18bb643d124b8b9ec3b1f62b081f044611/src/utils/internal/event-stream.ts#L170-L187product
https://github.com/h3js/h3/commit/7791538e15ca22437307c06b78fa155bb73632a6patch
https://github.com/h3js/h3/security/advisories/GHSA-22cc-p3c6-wpvmexploit, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.