CVE-2026-9986Network attack vector

UI spoofing via unvalidated OptimizationGuide input

Published May 28, 2026 · Updated May 28, 2026

Insufficient input validation in Google Chrome OptimizationGuide before 148.0.7778.216 allows remote attackers to spoof UI via crafted HTML. Public records do not disclose which OptimizationGuide input or validation operation is defective, and the linked Chromium issue remains restricted. The renderer must already be compromised, and the resulting spoofing can misrepresent browser content to an interacting user; no stronger impact is published.

CVSS severity4.2
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient input validation in Google Chrome OptimizationGuide before 148.0.7778.216 allows remote attackers to spoof UI via crafted HTML. Public records do not disclose which OptimizationGuide input or validation operation is defective, and the linked Chromium issue remains restricted. The renderer must already be compromised, and the resulting spoofing can misrepresent browser content to an interacting user; no stronger impact is published.

The record

CVE
CVE-2026-9986
Published
May 28, 2026
Updated
May 28, 2026
Vendor
Go standard library
Product
Google Chrome
Classifications
CWE-20
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 28, 2026CVE publishedPublication date reported by the CVE source.
  2. May 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=148.0.7778.216 <148.0.7778.216

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Go standard library · Google Chromeversion=148.0.7778.216 <148.0.7778.216

Published CVSS scores

4.2CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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