CVE-2025-29834: Microsoft Edge Chromium RCE Vulnerability

CVE-2025-29834 Overview

CVE-2025-29834 is an out-of-bounds read vulnerability [CWE-125] in Microsoft Edge (Chromium-based). The flaw allows an unauthenticated attacker to execute code remotely over a network. Exploitation requires user interaction, such as visiting a malicious web page or opening a crafted document that renders in Edge.

Microsoft published the advisory on April 12, 2025. The vulnerability carries a CVSS 3.1 base score of 7.5 with attack vector Network. The EPSS probability is 0.528% at the 67.354 percentile, indicating moderate likelihood of exploit activity relative to other CVEs.

Critical Impact

An attacker who successfully exploits CVE-2025-29834 can execute arbitrary code in the context of the browser process, compromising confidentiality, integrity, and availability of the affected system.

Affected Products

• Microsoft Edge (Chromium-based) — all versions prior to the April 2025 security update
• Windows installations running vulnerable Edge builds
• macOS and Linux installations running vulnerable Edge builds

Discovery Timeline

• 2025-04-12 - CVE-2025-29834 published to the National Vulnerability Database
• 2025-04-12 - Microsoft Security Update Guide advisory released
• 2025-07-08 - Last updated in NVD database

Technical Details for CVE-2025-29834

Vulnerability Analysis

The vulnerability is an out-of-bounds read in the Chromium-based Microsoft Edge browser. Out-of-bounds read flaws occur when code accesses memory outside the bounds of an allocated buffer. In a browser context, this typically arises in components that parse untrusted data such as HTML, JavaScript, image formats, fonts, or media streams.

Microsoft's advisory indicates the condition can be leveraged for remote code execution. This pattern is consistent with read primitives that leak adjacent memory contents, which an attacker chains with additional bugs or memory grooming to control execution flow. The attack complexity is rated High because reliable exploitation requires specific memory layout conditions.

User interaction is required. The attacker must convince a victim to navigate to attacker-controlled content rendered by Edge.

Root Cause

The root cause is missing or insufficient bounds checking on a buffer read operation within Edge's Chromium-based rendering or processing code [CWE-125]. Microsoft has not publicly disclosed the specific component or function involved. Refer to the Microsoft Security Update Guide CVE-2025-29834 for vendor details.

Attack Vector

The attack is delivered over the network. A typical exploitation chain involves the attacker hosting a malicious web page or embedding crafted content in an iframe, advertisement, or document. When a user opens the content in a vulnerable Edge build, the out-of-bounds read is triggered, and combined with additional primitives yields code execution in the renderer or browser process.

No public proof-of-concept exploit, ExploitDB entry, or CISA KEV listing is associated with CVE-2025-29834 at the time of writing.

// No verified exploit code is publicly available for CVE-2025-29834.
// Refer to the Microsoft Security Update Guide for vendor-supplied technical details.

Detection Methods for CVE-2025-29834

Indicators of Compromise

• Unexpected Edge renderer or msedge.exe process crashes correlated with browsing activity, often visible in Windows Error Reporting and Application event logs
• Edge child processes spawning unexpected children such as cmd.exe, powershell.exe, or rundll32.exe
• Outbound network connections from Edge processes to newly registered or low-reputation domains immediately after page loads

Detection Strategies

• Inventory Edge versions across the fleet and flag endpoints running builds released before the April 2025 cumulative update
• Hunt for browser exploitation patterns: renderer process anomalies, suspicious child process trees rooted at msedge.exe, and unsigned module loads inside browser processes
• Correlate web proxy logs with endpoint telemetry to identify users who visited suspicious URLs preceding browser crashes

Monitoring Recommendations

• Enable and forward Edge crash telemetry and Windows Error Reporting events to a central SIEM
• Monitor process creation events (Sysmon Event ID 1, Windows 4688) for unusual children of msedge.exe
• Track Edge auto-update status across managed endpoints and alert when versions fall out of compliance

How to Mitigate CVE-2025-29834

Immediate Actions Required

• Update Microsoft Edge to the latest stable channel build released on or after April 12, 2025
• Verify Edge auto-update is enabled and functioning on all managed endpoints
• Restrict browsing to trusted sites on systems that cannot be patched immediately

Patch Information

Microsoft addressed CVE-2025-29834 in the April 2025 Edge stable channel update. Administrators should consult the Microsoft Security Update Guide CVE-2025-29834 for the fixed version number and deployment guidance. Edge typically updates automatically; managed environments using Microsoft Edge Update policies should confirm the policy permits the rollout.

Workarounds

• Use an alternate, fully patched browser on hosts where Edge cannot be updated
• Apply web filtering and SmartScreen policies to block access to high-risk and untrusted domains
• Enforce the principle of least privilege so browser compromise does not yield administrative access

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

# Force an Edge update check via the Edge Update service
"%ProgramFiles(x86)%\Microsoft\EdgeUpdate\MicrosoftEdgeUpdate.exe" /ua /installsource scheduler