Bug 2529158 (CVE-2026-86252)

Summary: CVE-2026-86252 h3: h3: Server-Sent Events (SSE) injection via carriage return
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in h3. This vulnerability allows a remote attacker to inject arbitrary Server-Sent Events (SSE) by failing to sanitize carriage return characters in EventStream data and comment fields. Attackers can manipulate event type directives, split single push calls into multiple browser-parsed events, or escape comment fields to inject data, potentially leading to integrity issues.
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Description OSIDB Bzimport 2026-09-06 12:11:39 UTC 
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.