CVE-2026-33128

Q: Is CVE-2026-33128 being actively exploited?

Not that we know of. CVE-2026-33128 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.57% is the estimated probability that it will be exploited in the next 30 days. That is higher than 44% of all scored CVEs.

Q: How severe is CVE-2026-33128?

CVE-2026-33128 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2026-33128 affect?

Published advisories record a fix for h3 (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

HIGH

7.5

CVSS v3

NVD

Description

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.

CWE-93

How to fix

Remediation Available

h3NVD

Affected:< 1.15.6Fixed in:1.15.6CVE-2026-33128derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeChanged

Impact

ConfidentialityLow

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

Exploit Intelligence

0.57%probability of exploitation in 30 days

44thpercentile

Moderate risk: more likely to be exploited than 44% of all known CVEs.

References

Patch1

github.com

Exploit1

github.com

Product1

github.com

Related Vulnerabilities

Other CWE-93 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-61884	High	7.5	98%	KEV + Ransom	-
CVE-2022-0666	High	7.5	44%	-	Fix
CVE-2016-3115	Medium	6.4	37%	-	Fix
CVE-2024-20337	High	8.2	30%	-	Fix
CVE-2021-39172	High	8.8	29%	-	Fix
CVE-2016-4975	Medium	6.1	20%	-	Fix

Common questions

How do I fix CVE-2026-33128?

Upgrade h3 to 1.15.6 or later.

Is CVE-2026-33128 being actively exploited?

Not that we know of. CVE-2026-33128 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.57% is the estimated probability that it will be exploited in the next 30 days. That is higher than 44% of all scored CVEs.

How severe is CVE-2026-33128?

CVE-2026-33128 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-33128 affect?

Published advisories record a fix for h3 (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

Embed a live status badge for CVE-2026-33128

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-03-20.