What is the CVSS score of CVE-2026-9986?

CVE-2026-9986 has a CVSS 3.1 base score of 4.2 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:L. EPSS exploitation probability: 0.0%.

Is there a patch available for CVE-2026-9986?

Yes, a patch is available for CVE-2026-9986. Update the affected software to the latest version immediately.

Google Chrome CVE-2026-9986

EUVD-2026-33128 MEDIUM

Improper Input Validation (CWE-20)

2026-05-28 Chrome

GHSA-g8q5-42mc-pjxg

Information Disclosure Google

4.2

CVSS 3.1 · Vendor: Chrome

Severity by source

Vendor (Chrome) PRIMARY

4.2 MEDIUM

AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:L

SUSE

MEDIUM

qualitative

Red Hat

5.7 HIGH

qualitative

Primary rating from Vendor (Chrome).

CVSS VectorVendor: Chrome

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

Low

Lifecycle Timeline

Analysis Generated

May 29, 2026 - 18:30 vuln.today

CVSS changed

May 29, 2026 - 18:22 NVD

4.2 (MEDIUM)

CVE Published

May 28, 2026 - 22:25 nvd

MEDIUM 4.2

CVE Published

May 28, 2026 - 22:25 nvd

UNKNOWN (no severity yet)

DescriptionCVE.org

Insufficient validation of untrusted input in OptimizationGuide in Google Chrome prior to 148.0.7778.216 allowed a remote attacker who had compromised the renderer process to perform UI spoofing via a crafted HTML page. (Chromium security severity: High)

AnalysisAI

UI spoofing in Google Chrome's OptimizationGuide component (all versions prior to 148.0.7778.216) enables a remote unauthenticated attacker who has already compromised the renderer process to present false browser UI elements to the user via a crafted HTML page. The root cause is CWE-20 (Improper Input Validation) - OptimizationGuide fails to adequately validate untrusted data sourced from the renderer, allowing that data to influence trusted browser UI surfaces. With a CVSS score of 4.2, EPSS at 0.05% (15th percentile), no KEV listing, and no public exploit identified at time of analysis, real-world risk is moderate-low despite the network vector, heavily gated by the renderer-compromise prerequisite.

Technical ContextAI

OptimizationGuide is a Chrome subsystem responsible for delivering machine-learning-based performance hints, model inference, and optimization signals to various browser components. It sits at the boundary between the renderer (sandboxed, lower-trust) and the browser process (higher-trust), making it a meaningful target for sandbox-escape or cross-context manipulation. CWE-20 (Improper Input Validation) at this boundary means that renderer-supplied data is passed into OptimizationGuide without sufficient sanitization or trust enforcement, allowing it to influence browser UI rendering in unintended ways. The CPE cpe:2.3:a:google:chrome:*:*:*:*:*:*:*:* confirms this affects the desktop Chrome application across platforms. The CVSS vector AV:N/AC:H/PR:N/UI:R/S:U reflects a network-delivered attack requiring prior renderer compromise (captured in AC:H) and a user visiting a crafted page (UI:R), with unchanged scope indicating the exploit does not itself escape to the OS layer.

RemediationAI

Vendor-released patch: Chrome 148.0.7778.216. Update Google Chrome to version 148.0.7778.216 or later immediately via the browser's built-in update mechanism (Help > About Google Chrome) or through enterprise deployment tools (GPO, Google Admin Console). The fix is confirmed in the official Stable Channel Update advisory at https://chromereleases.googleblog.com/2026/05/stable-channel-update-for-desktop_0877304591.html. Because exploitation requires a prior renderer compromise, organizations that enforce Chrome's Site Isolation feature (enabled by default in modern Chrome) and keep renderer sandboxing intact reduce the practical exploitability of this and similar second-stage UI spoofing issues. Restricting access to untrusted or high-risk web content through enterprise web filtering provides an additional compensating control while updates are being deployed, at the cost of potential productivity impact from over-blocking. No workaround eliminates the vulnerability - patching is the only definitive fix.