CRLF Injection Affecting h3 package, versions <1.15.6>=2.0.0 <2.0.1-rc.15
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-H3-15692480
- published19 Mar 2026
- disclosed18 Mar 2026
- credit0xkakash1
Introduced: 18 Mar 2026
CVE-2026-33128 (opens in a new tab)How to fix?
Upgrade h3 to version 1.15.6, 2.0.1-rc.15 or higher.
Overview
h3 is a Minimal H(TTP) framework built for high performance and portability.
Affected versions of this package are vulnerable to CRLF Injection via unsanitized input in the formatEventStreamMessage and formatEventStreamComment functions. An attacker can inject arbitrary Server-Sent Events (SSE) fields or events to connected clients by supplying newline characters in the id, event, data, or comment fields, which can lead to cross-user content injection, phishing, event spoofing, forced client reconnections, or manipulation of event replay behavior.