CVE-2026-86252

Exploitation

Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.

SSVC decision

• ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
• AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
• Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.36% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 29.5% of scored records. A rank, not a probability.

NVD base score

6.9 (CVSS v4.0), scored by the NVD independently of the CNA.

NVD CVSS vector

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

NVD analysis status

Awaiting Analysis. NVD last modified this record on 2026-09-08.

Red Hat severity

Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-09-06 12:00Z1 MO AGO

Last updated

2026-09-08 15:13Z1 MO AGO

Reserved

2026-09-06

Assigning CNA

VulnCheck

Record state

PUBLISHED

Severity

Medium (CVSS 6.9)

CNA CVSS vector

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

Weaknesses

• CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')Class
• CWE-93Improper Neutralization of CRLF Sequences ('CRLF Injection')Base

Data version

5.2

Document digest

b470547c95d7d83cc5dbd396b315705006eb1a20aef4a400013b1ef1c4baa3d8

• github.comGitHub Security Advisory (GHSA-4hxc-9384-m385)https://github.com/h3js/h3/security/advisories/GHSA-4hxc-9384-m385vendor-advisory
• www.vulncheck.comVulnCheck Advisory: h3 before 1.15.9 SSE Event Injection via Carriage Returnhttps://www.vulncheck.com/advisories/h3-before-1.15.9-sse-event-injection-via-carriage-returnthird-party-advisory