CVE-2026-86252 (GCVE-0-2026-86252)
Vulnerability from cvelistv5 – Published: 2026-09-06 12:00 – Updated: 2026-09-06 12:00
VLAI
EPSS
VEX
Title
h3 before 1.15.9 SSE Event Injection via Carriage Return
Summary
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.
Severity
5.3 (Medium)
CWE
- CWE-74 - Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/h3js/h3/security/advisories/GH… | vendor-advisory |
| https://www.vulncheck.com/advisories/h3-before-1.… | third-party-advisory |
Impacted products
Date Public
2026-03-20 00:00
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}
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"description": "Improper Neutralization of Special Elements in Output Used by a Downstream Component (\u0027Injection\u0027)",
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]
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"references": [
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"name": "GitHub Security Advisory (GHSA-4hxc-9384-m385)",
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],
"url": "https://github.com/h3js/h3/security/advisories/GHSA-4hxc-9384-m385"
},
{
"name": "VulnCheck Advisory: h3 before 1.15.9 SSE Event Injection via Carriage Return",
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],
"url": "https://www.vulncheck.com/advisories/h3-before-1.15.9-sse-event-injection-via-carriage-return"
}
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"title": "h3 before 1.15.9 SSE Event Injection via Carriage Return",
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"datePublished": "2026-09-06T12:00:27.561Z",
"dateReserved": "2026-09-06T11:35:19.316Z",
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}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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