CVE-2026-45495: Microsoft Edge Chromium RCE Vulnerability

CVE-2026-45495 Overview

CVE-2026-45495 is a remote code execution vulnerability in Microsoft Edge (Chromium-based). The flaw stems from improper input validation [CWE-20] within the browser. Attackers can exploit the vulnerability over the network without authentication or user interaction, enabling arbitrary code execution in the context of the browser process.

Microsoft published the advisory through the Microsoft Security Response Center (MSRC) update guide. The vulnerability affects the Chromium-based version of Microsoft Edge across supported platforms.

Critical Impact

Successful exploitation grants attackers full code execution on the victim system with high impact to confidentiality, integrity, and availability — all reachable over the network without privileges or user interaction.

Affected Products

• Microsoft Edge (Chromium-based) — all versions prior to the MSRC-listed fixed build
• Windows desktop installations running Microsoft Edge Chromium
• macOS and Linux distributions of Microsoft Edge Chromium

Discovery Timeline

• 2026-05-18 - CVE-2026-45495 published to the National Vulnerability Database (NVD)
• 2026-05-19 - Last updated in NVD database

Technical Details for CVE-2026-45495

Vulnerability Analysis

The vulnerability is categorized as improper input validation [CWE-20] in Microsoft Edge's Chromium-based engine. The browser fails to correctly validate untrusted input before processing it. This validation gap allows attacker-controlled data to influence execution paths inside the renderer or browser process.

The attack vector is network-based and requires no authentication. Microsoft classifies the issue as remote code execution, meaning attackers can run arbitrary code on the target system after exploitation. The Microsoft Security Response Center has not disclosed exploitation details to limit weaponization risk.

No public proof-of-concept exploit exists at the time of publication. The vulnerability is not listed on the CISA Known Exploited Vulnerabilities catalog and EPSS data does not indicate active exploitation activity.

Root Cause

The root cause is improper input validation within a component of Microsoft Edge Chromium. The component accepts data from untrusted sources, such as remote web content, without sufficient checks on type, size, or structure. Malformed input reaches downstream parsing or memory operations and corrupts execution state.

Attack Vector

Exploitation requires the victim to load attacker-controlled web content in Microsoft Edge. An attacker hosts a malicious page or compromises a legitimate site to deliver the payload. Once the browser parses the crafted input, the validation flaw triggers code execution in the browser's process context. Refer to the Microsoft CVE-2026-45495 Update Guide for vendor technical context.

No verified exploit code is publicly available. The vulnerability mechanism is described in prose only; see the vendor advisory for further details.

Detection Methods for CVE-2026-45495

Indicators of Compromise

• Unexpected child processes spawned by msedge.exe, particularly command shells, scripting hosts, or rundll32.exe
• Outbound network connections from Edge processes to uncategorized or newly registered domains shortly after page loads
• Edge crashes or repeated renderer process restarts correlated with specific URLs in browser history

Detection Strategies

• Monitor process lineage where msedge.exe is the parent of non-browser binaries, which is anomalous for normal browsing
• Inspect web proxy and DNS telemetry for users visiting low-reputation domains followed by endpoint anomalies
• Correlate browser crash telemetry from Windows Error Reporting with subsequent suspicious process activity on the same host

Monitoring Recommendations

• Enable EDR process and command-line auditing on all endpoints running Microsoft Edge
• Forward browser, DNS, and proxy logs to a centralized SIEM for cross-source correlation
• Track Microsoft Edge version inventory across managed endpoints and alert on hosts running pre-patch builds

How to Mitigate CVE-2026-45495

Immediate Actions Required

• Update Microsoft Edge to the fixed version listed in the Microsoft CVE-2026-45495 Update Guide
• Verify automatic Edge updates are enabled through group policy or Intune across the fleet
• Restrict browsing to trusted destinations for high-value accounts until patches are deployed organization-wide

Patch Information

Microsoft has released a security update through the Microsoft Edge servicing channel. Administrators should consult the Microsoft CVE-2026-45495 Update Guide for the exact fixed build number and deployment guidance. Edge typically updates automatically, but enterprise environments using update deferral policies must validate rollout.

Workarounds

• Deploy strict web filtering and DNS reputation controls to reduce exposure to attacker-hosted pages
• Apply Microsoft Edge security baselines that restrict legacy renderer features and disable unnecessary extensions
• Enforce least-privilege user accounts so browser-context code execution cannot escalate to administrative actions

# Force Microsoft Edge update check on Windows endpoints
"%ProgramFiles(x86)%\Microsoft\EdgeUpdate\MicrosoftEdgeUpdate.exe" /ua /installsource scheduler

# Verify installed Microsoft Edge version
reg query "HKLM\SOFTWARE\Microsoft\Edge\BLBeacon" /v version