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.
CVE-2026-33128
CRITICALNVD 10.010.0Trending — 3 sources updated this week
EchelonGraph scoreLOW confidence
This critical-severity CVE scores 10.0 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: nvd
10.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 10.0Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 10.0
- EG Score
- 10.0(low)
- EG Risk
- 50(Track)EG Risk 50/100SSVC: 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 computedSeverity100% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 1%
- EPSS %ILE
- 44%
- KEV
- Not listed
Published
March 20, 2026
Last Modified
June 17, 2026
Advisory Details (3)
Auto-updated Jul 27, 2026🔬 Proof of concept available. Patch available. Sources: github_commit, github.
github Patch Available🟡 PoC Available
Server-Sent Events Injection via Unsanitized Newlines in Event Stream Fields · Advisory · h3js/h3 · GitHub
https://github.com/h3js/h3/security/advisories/GHSA-22cc-p3c6-wpvmgithub_commit Patch Available
commit 7791538e15ca (h3js/h3)
Patch available: h3js/h3 v2.0.1-rc.15 (contains commit 7791538e15ca)
https://github.com/h3js/h3/commit/7791538e15ca22437307c06b78fa155bb73632a6generic
h3/src/utils/internal/event-stream.ts at 52c82e18bb643d124b8b9ec3b1f62b081f044611 · h3js/h3 · GitHub
https://github.com/h3js/h3/blob/52c82e18bb643d124b8b9ec3b1f62b081f044611/src/utils/internal/event-stream.ts#L170-L187Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 5× in last 7d / 5× 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.
- 2026-08-01 04:16 UTCEPSS rescore
- 2026-07-30 16:28 UTCEPSS rescore
- 2026-07-30 01:30 UTCEPSS rescore
- 2026-07-27 14:35 UTCEG score recompute
- 2026-07-27 14:27 UTCOSV refresh
Frequently asked(5)
What is CVE-2026-33128?
CVE-2026-33128 is a critical vulnerability published on March 20, 2026. 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…
When was CVE-2026-33128 disclosed?
CVE-2026-33128 was first published in the National Vulnerability Database on March 20, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33128 actively exploited?
CVE-2026-33128 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 55.9% of all scored CVEs.
What is the CVSS score of CVE-2026-33128?
CVE-2026-33128 has a CVSS v3 base score of 10.0 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-33128?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33128, 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.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-33128
Is Your Infrastructure Affected by CVE-2026-33128?
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