CVE-2026-6305 Overview
A heap buffer overflow vulnerability has been identified in PDFium, the PDF rendering engine used by Google Chrome. This vulnerability exists in Google Chrome versions prior to 147.0.7727.101 and allows a remote attacker to execute arbitrary code inside the browser sandbox by tricking a user into opening a specially crafted PDF file. The vulnerability has been classified with high Chromium security severity.
Critical Impact
Remote attackers can achieve arbitrary code execution within the Chrome sandbox by delivering malicious PDF files, potentially leading to further exploitation or sandbox escape when combined with other vulnerabilities.
Affected Products
- Google Chrome versions prior to 147.0.7727.101
- Chromium-based browsers using vulnerable PDFium versions
- Applications embedding the affected PDFium library
Discovery Timeline
- 2026-04-15 - CVE-2026-6305 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2026-6305
Vulnerability Analysis
This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow), a memory corruption issue that occurs when data is written beyond the allocated boundaries of a heap buffer. In the context of PDFium, the heap overflow manifests during the processing of malformed PDF structures, where improper boundary validation allows an attacker to corrupt adjacent heap memory.
The network-based attack vector requires user interaction—specifically, the victim must open or preview a malicious PDF file. Once triggered, the overflow can overwrite critical heap metadata or adjacent objects, enabling an attacker to gain control of program execution flow within the sandbox environment.
Root Cause
The root cause of CVE-2026-6305 lies in insufficient bounds checking within PDFium's PDF parsing routines. When processing certain PDF object streams or embedded resources, the renderer fails to properly validate the size of input data against the allocated buffer capacity. This oversight allows specially crafted PDF content to trigger a write operation that exceeds the intended buffer boundaries, corrupting heap memory structures.
Attack Vector
The attack is executed remotely over the network, requiring an attacker to deliver a malicious PDF file to the victim. Common delivery mechanisms include:
- Email attachments containing weaponized PDF documents
- Drive-by downloads from compromised or malicious websites
- Malicious advertisements serving PDF content
- Social engineering attacks via messaging platforms
When a victim opens the crafted PDF in a vulnerable Chrome browser, the malformed content triggers the heap overflow during rendering. While the code execution occurs within Chrome's sandbox, this vulnerability could potentially be chained with sandbox escape vulnerabilities for complete system compromise.
The vulnerability mechanism involves the PDF parser mishandling object stream boundaries during content rendering. For complete technical analysis, refer to the Chromium Issue Tracker Entry once the security restriction period ends.
Detection Methods for CVE-2026-6305
Indicators of Compromise
- Unexpected Chrome process crashes when opening PDF files
- Anomalous memory consumption patterns in Chrome renderer processes
- PDF files with unusually structured or oversized object streams
- Network traffic downloading PDF files from known malicious domains
Detection Strategies
- Monitor for Chrome crash reports related to PDFium or PDF rendering components
- Implement network-level inspection for malformed PDF files at email and web gateways
- Deploy endpoint detection rules that flag unusual memory access patterns in browser processes
- Track Chrome version compliance across enterprise environments to identify vulnerable installations
Monitoring Recommendations
- Enable Chrome's built-in crash reporting and monitor for PDFium-related crashes
- Implement application allowlisting to control PDF viewers in sensitive environments
- Configure SIEM rules to correlate PDF downloads with subsequent suspicious browser behavior
- Establish baseline browser performance metrics to detect anomalous resource consumption
How to Mitigate CVE-2026-6305
Immediate Actions Required
- Update Google Chrome to version 147.0.7727.101 or later immediately
- Enable automatic updates for Chrome across all managed endpoints
- Audit enterprise environments for vulnerable Chrome versions using asset management tools
- Consider temporarily disabling PDF preview functionality in Chrome for high-risk environments
Patch Information
Google has released Chrome version 147.0.7727.101 which addresses this heap buffer overflow vulnerability in PDFium. Organizations should prioritize this update due to the potential for arbitrary code execution. The security patch details are available in the Google Chrome Update Announcement.
For enterprise deployments, administrators can push the update through Chrome Enterprise policies or utilize software deployment tools to ensure all endpoints are patched. Verify successful patching by checking the Chrome version via chrome://version.
Workarounds
- Configure Chrome to download PDFs instead of rendering them inline using chrome://settings/content/pdfDocuments
- Use alternative PDF readers that are not affected by this vulnerability
- Implement strict email attachment filtering to quarantine PDF files from untrusted sources
- Deploy browser isolation solutions to contain potential exploitation attempts
# Verify Chrome version and check for updates
google-chrome --version
# Enterprise deployment - force Chrome update via policy
# Add to Chrome policy template:
# "BrowserSignin": 1
# "AutoUpdateCheckPeriodMinutes": 60
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
