CVE-2026-4455: Google Chrome Buffer Overflow Vulnerability

CVE-2026-4455 Overview

A heap buffer overflow vulnerability has been identified in PDFium, the PDF rendering engine used by Google Chrome. This memory corruption flaw exists in Chrome versions prior to 146.0.7680.153 and can be triggered when the browser processes a specially crafted PDF file. The vulnerability allows remote attackers to potentially exploit heap corruption, which could lead to arbitrary code execution in the context of the browser process.

Critical Impact

Remote attackers can exploit this heap buffer overflow to potentially achieve code execution by enticing users to open malicious PDF files, compromising system integrity across Windows, macOS, and Linux platforms.

Affected Products

• Google Chrome versions prior to 146.0.7680.153
• Apple macOS (Chrome installations)
• Linux (Chrome installations)
• Microsoft Windows (Chrome installations)

Discovery Timeline

• 2026-03-20 - CVE-2026-4455 published to NVD
• 2026-03-20 - Last updated in NVD database

Technical Details for CVE-2026-4455

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow), a critical memory corruption issue that occurs when a program writes data beyond the allocated boundaries of a heap buffer. In the context of PDFium, the heap overflow is triggered during the parsing or rendering of PDF content, where insufficient bounds checking allows an attacker-controlled PDF to write past the end of an allocated memory region.

The exploitation scenario requires user interaction—a victim must open a malicious PDF file either directly in Chrome or through a web page that embeds the malicious PDF. Once triggered, the heap corruption can overwrite adjacent heap metadata or application data, potentially allowing an attacker to gain control of program execution flow.

Root Cause

The root cause lies in improper memory management within the PDFium library when processing certain PDF structures. Specifically, the vulnerable code path fails to properly validate the size of data being written to a heap-allocated buffer, allowing content from a maliciously crafted PDF to overflow the buffer boundaries. This type of vulnerability typically occurs when array indices or buffer sizes are calculated incorrectly, or when length checks are missing entirely before memory copy operations.

Attack Vector

The attack vector for CVE-2026-4455 is network-based, requiring an attacker to deliver a malicious PDF file to the victim. Common attack scenarios include:

1. Phishing campaigns - Sending emails with malicious PDF attachments or links to websites hosting the exploit PDF
2. Watering hole attacks - Compromising legitimate websites to serve malicious PDFs to targeted visitors
3. Drive-by downloads - Embedding malicious PDFs in web pages that automatically load when users visit

The vulnerability does not require any privileges on the target system but does require user interaction to open the malicious PDF. Once the PDF is processed by Chrome's PDFium component, the heap overflow occurs, potentially leading to arbitrary code execution with the privileges of the browser process.

The exploitation mechanism involves crafting PDF stream objects or font data with carefully calculated sizes that trigger the overflow condition. Technical details regarding the specific vulnerable function can be found in the Chromium Issue Tracker #488585504.

Detection Methods for CVE-2026-4455

Indicators of Compromise

• Unexpected Chrome crashes or hangs when opening PDF files
• Memory access violations or heap corruption errors in Chrome crash logs
• Suspicious PDF files with unusual stream object sizes or malformed font tables
• Chrome processes spawning unexpected child processes after PDF interaction

Detection Strategies

• Monitor for abnormal memory allocation patterns in Chrome browser processes
• Implement network-based detection for known malicious PDF structures targeting PDFium
• Deploy endpoint detection rules that alert on heap corruption indicators in browser contexts
• Analyze PDF files at the gateway for suspicious embedded content before delivery to endpoints

Monitoring Recommendations

• Enable Chrome's built-in crash reporting and review crash dumps for heap corruption signatures
• Monitor security telemetry for attempted exploitations matching PDFium vulnerability patterns
• Track Chrome version deployments across the organization to identify unpatched instances
• Implement browser isolation for high-risk users to contain potential exploitation

How to Mitigate CVE-2026-4455

Immediate Actions Required

• Update Google Chrome to version 146.0.7680.153 or later immediately
• Enable automatic updates in Chrome to receive future security patches promptly
• Consider blocking PDF file downloads and email attachments temporarily in high-risk environments
• Implement browser isolation technologies to limit the impact of potential exploitation

Patch Information

Google has released a security update that addresses this vulnerability in Chrome version 146.0.7680.153. The patch includes proper bounds checking in the affected PDFium code paths to prevent heap buffer overflow conditions. Organizations should prioritize deployment of this update across all managed Chrome installations.

For detailed information about the security update, refer to the Google Chrome Stable Channel Update announcement.

Workarounds

• Disable Chrome's built-in PDF viewer and use an alternative PDF reader application
• Configure email gateways to quarantine PDF attachments pending security review
• Implement strict Content Security Policy headers to prevent automatic PDF loading on web pages
• Use browser extensions that block automatic PDF rendering until user approval

# Disable Chrome PDF viewer via policy (Windows Registry)
# HKLM\SOFTWARE\Policies\Google\Chrome
# AlwaysOpenPdfExternally = 1

# For enterprise deployment, use Group Policy or Chrome Enterprise policies
# to enforce PDF viewer settings across managed devices