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TI-2026-59038 Aliases CVE-2026-86252GHSA-jqj6-8hxr-7wwq

h3 before 1.15.9 SSE Event Injection via Carriage Return

Priority HIGH 70CWE-74Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
—
Confidentiality · integrity · availability
None · Low · None
Fix status
Partial Red Hat: 1 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat.

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0036 30th percentileScored 2026-11-07
Fix Partial h3 (h3js): 1.15.9, 2.0.1-rc.17Red Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
h3jsh3before 1.15.9; 2.0.0-beta.0 to before 2.0.1-rc.171.15.9, 2.0.1-rc.17Patch availableCNA
  • h3 Vendorh3js Affected before 1.15.9; 2.0.0-beta.0 to before 2.0.1-rc.17 Fixed in 1.15.9, 2.0.1-rc.17 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:h3:h3:*:*:*:*:*:*:*:*——h3js
  • cpe:2.3:a:h3:h3:*:*:*:*:*:*:*:* Versions — — ·h3js

Remediation

  • Fix · CNA h3 (h3js) Fixed in 1.15.9, 2.0.1-rc.17

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet: Fix deferred

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-86252
  2. 2026-10-03 Alias added: GHSA-jqj6-8hxr-7wwq

References

Advisory 1

  • TI-2026-25559 h3 has a Server-Sent Events Injection via Unsanitized Newlines in Event Stream Fields CVSS 3.1CRITICAL 10.0
  • TI-2026-25562 h3 has a middleware bypass with one gadget CVSS 3.1CRITICAL 9.1
  • TI-2026-59037 h3 before 1.15.9 Path Traversal via Double Decoding CVSS 4.0HIGH 8.2
  • TI-2026-25560 h3 has an observable timing discrepancy in basic auth utils CVSS 3.1MEDIUM 5.9
  • TI-2026-58994 h3 before 2.0.1-rc.18 Open Redirect via redirectBack() CVSS 4.0MEDIUM 5.3
  • TI-2026-25886 h3: Missing Path Segment Boundary Check in `mount()` Causes Middleware Execution on Unrelated Prefix-Matching Routes CVSS 3.1MEDIUM 5.3
See all 10 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences