CVE-2026-86252

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    CVE-2026-86252

    Published: 6 Sept 2026Last Modified: 10 Sept 2026

    Summary: h3 before 1.15.9 SSE Event Injection via Carriage Return

    Details: 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.

    References: https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86252.json, https://github.com/h3js/h3/security/advisories/GHSA-4hxc-9384-m385, https://nvd.nist.gov/vuln/detail/CVE-2026-86252, https://www.vulncheck.com/advisories/h3-before-1.15.9-sse-event-injection-via-carriage-return

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 0
    Fixed -4e8d43a7703d0d5c8bbc09748db1d8b9f3c51b42

    Affected versions

    v1.15.8
    v1.15.7
    v1.15.6
    v1.15.5
    v1.15.4
    v1.15.2
    v1.15.1
    v1.15.0

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2026-86252 | CVE-DB