CVE-2026-57974: Microsoft Edge Chromium RCE Vulnerability

CVE-2026-57974 Overview

CVE-2026-57974 is an integer overflow vulnerability [CWE-190] in Microsoft Edge (Chromium-based) that enables remote code execution. An unauthorized attacker can execute arbitrary code over a network by convincing a user to visit a crafted web page. The flaw carries a CVSS 3.1 score of 8.8 and requires user interaction to trigger.

Microsoft published guidance for this issue in the Microsoft Security Update Guide. No public proof-of-concept exploit or in-the-wild exploitation has been reported at the time of publication.

Critical Impact
Successful exploitation grants remote code execution in the context of the browser process, exposing browsing sessions, credentials, and local resources reachable by the affected user.

Affected Products

Microsoft Edge (Chromium-based)
CPE: cpe:2.3:a:microsoft:edge_chromium:*:*:*:*:-:*:*:*
Component: microsoft:edge_chromium

Discovery Timeline

2026-07-03 - CVE-2026-57974 published to NVD
2026-07-07 - Last updated in NVD database

Technical Details for CVE-2026-57974

Vulnerability Analysis

The vulnerability is classified under [CWE-190] Integer Overflow or Wraparound. Integer overflows occur when an arithmetic operation produces a value that exceeds the storage size of its integer type, causing the value to wrap around to an unexpected number. In a browser context, this typically leads to undersized memory allocations followed by out-of-bounds writes that corrupt adjacent heap structures.

An attacker who chains the wrap-around with a controllable write primitive can hijack execution flow inside the Edge renderer or another affected process. The attack vector is network-based and does not require authentication, but user interaction is required, meaning the target must load attacker-controlled content in the browser.

The scope is unchanged, and confidentiality, integrity, and availability are all rated high. This aligns with a memory corruption bug that yields code execution rather than a sandbox escape or privilege boundary crossing.

Root Cause

The defect stems from arithmetic on an unchecked integer used to size a buffer or index a memory region. When the computed value wraps past the maximum of its type, the subsequent allocation or bounds check operates on a truncated size. Attackers supply crafted inputs that force the overflow, then write beyond the allocated region.

Attack Vector

Exploitation follows the standard drive-by download pattern for Chromium browser bugs. The attacker hosts a malicious page or delivers crafted content through advertising, iframes, or compromised sites. When the victim visits the page, the browser processes attacker-controlled data that triggers the integer overflow, corrupts memory, and pivots to code execution in the browser process.

See the Microsoft Security Update Guide entry for CVE-2026-57974 for vendor-supplied technical detail.

Detection Methods for CVE-2026-57974

Indicators of Compromise

Unexpected child processes spawned by msedge.exe, particularly command shells, powershell.exe, cmd.exe, or rundll32.exe.
Edge renderer or browser process crashes with access violations shortly after visiting a specific URL.
Outbound network connections from msedge.exe to unfamiliar domains or IP addresses that do not correspond to normal browsing activity.
New persistence entries created in the user context immediately following browser activity.

Detection Strategies

Monitor for process lineage anomalies where msedge.exe is the parent of scripting or LOLBin executables.
Alert on Edge renderer crash telemetry and Windows Error Reporting entries referencing integer overflow or heap corruption signatures.
Correlate browsing telemetry with endpoint identifications of shellcode-like memory allocations (RWX regions) inside Edge processes.

Monitoring Recommendations

Ingest Microsoft Defender SmartScreen and Edge browsing history into the SIEM to correlate URL visits with subsequent endpoint events.
Track Edge version inventory across the fleet and alert when unpatched builds remain deployed after Microsoft releases a fix.
Monitor EPSS trend data for CVE-2026-57974; the current EPSS probability is 0.556% at the 42.4 percentile, and any upward movement should trigger review.

How to Mitigate CVE-2026-57974

Immediate Actions Required

Update Microsoft Edge to the latest Stable channel build published by Microsoft in the advisory for CVE-2026-57974.
Verify automatic browser updates are enabled through Group Policy or Intune for all managed endpoints.
Restrict browsing to trusted sites for privileged accounts until patches are confirmed deployed.
Enable Enhanced Security Mode in Edge to enforce stricter mitigations such as Arbitrary Code Guard and Control Flow Guard on untrusted sites.

Patch Information

Microsoft has issued a security update through the Microsoft Security Update Guide for CVE-2026-57974. Edge updates ship through the standard Microsoft Edge update channel and Windows Update for Business. Confirm the running build matches or exceeds the fixed version listed in the advisory.

Workarounds

Deploy the MicrosoftEdgeUpdate policy to force update installation and disable version deferral.
Use network egress filtering and DNS-layer controls to block known malicious domains that host browser exploit kits.
Apply attack surface reduction rules that block child process creation from browser processes.

bash

# Verify installed Edge version on Windows endpoints
reg query "HKLM\SOFTWARE\Microsoft\EdgeUpdate\Clients\{56EB18F8-B008-4CBD-B6D2-8C97FE7E9062}" /v pv

# Force Edge update via command line
"%ProgramFiles(x86)%\Microsoft\EdgeUpdate\MicrosoftEdgeUpdate.exe" /ua /installsource scheduler