CVE-2026-86252h3 before 1.15.9 SSE Event Injection via Carriage Return
Updated under an hour ago ()
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It affects h3js h3. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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h3 versions before 1.15.9 fail to sanitize carriage return characters in EventStream data and comment fields, allowing attackers to inject arbitrary SSE events by including unsanitized carriage returns. Attackers can inject event type directives, split single push calls into multiple browser-parsed events, or escape comment fields to inject data, bypassing the prior CVE fix that only addressed newline injection.
- CVSS
- 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Weakness (CWE)
- CWE-74
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- VulnCheck
- NVD analysis
- Awaiting Analysis
- Record last updated
- Sep 8, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
h3js h3 h3js:h3 (from the name) | before 1.15.9; 1.15.9 not affected; from 2.0.0-beta.0 before 2.0.1-rc.17; 2.0.1-rc.17 not affected | CNA record |
References
- https://github.com/h3js/h3/security/advisories/GHSA-4hxc-9384-m385vendor-advisory
- https://www.vulncheck.com/advisories/h3-before-1.15.9-sse-event-injection-via-carriage-returnthird-party-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.