CVE-2026-86252CWE-74

CVE-2026-86252

Medium · published September 6, 2026

CVSS v3.1
5.3
EPSS
0%
Percentile
28.6
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS v4.0
6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
EPSS
0.00360 · 28.6th percentile
Weakness
CWE-74 · Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Published
2026-09-06T16:17Z
References (3)
https://github.com/h3js/h3/security/advisories/GHSA-4hxc-9384-m385 · [email protected]https://www.vulncheck.com/advisories/h3-before-1.15.9-sse-event-injection-via-carriage-return · [email protected]https://github.com/h3js/h3/security/advisories/GHSA-4hxc-9384-m385 · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 08 SEP 03:24Z
    EPSS moved — → 0%
    epss
  • 06 SEP 12:00Z
    h3 before 1.15.9 SSE Event Injection via Carriage Return
    cvelistv5