CVE-2026-11303: Google Chrome Use After Free Vulnerability

CVE-2026-11303 Overview

CVE-2026-11303 is a use-after-free vulnerability in PDFium, the PDF rendering engine bundled with Google Chrome. The flaw affects Chrome versions prior to 149.0.7827.53 across Windows, macOS, and Linux. A remote attacker can execute arbitrary code inside the Chrome sandbox by convincing a user to open a crafted PDF file. The vulnerability is tracked under CWE-416: Use After Free. Google's Chromium team rated the security severity as Low, but the National Vulnerability Database scores the issue at CVSS 8.8 (HIGH) due to the network attack vector and high impact on confidentiality, integrity, and availability.

Critical Impact
Successful exploitation allows arbitrary code execution within the Chrome renderer sandbox, providing a foothold for further sandbox-escape chains.

Affected Products

Google Chrome prior to 149.0.7827.53 on Microsoft Windows
Google Chrome prior to 149.0.7827.53 on Apple macOS
Google Chrome prior to 149.0.7827.53 on Linux

Discovery Timeline

2026-06-05 - CVE-2026-11303 published to NVD
2026-06-08 - Last updated in NVD database

Technical Details for CVE-2026-11303

Vulnerability Analysis

The vulnerability resides in PDFium, the open-source PDF parser and renderer integrated into Chrome. PDFium processes untrusted PDF content directly in the renderer process. A use-after-free condition occurs when the engine continues to reference a heap object after that object has been freed. An attacker who controls allocation and deallocation patterns through a crafted PDF can reclaim the freed memory with attacker-controlled data. The dangling pointer is then dereferenced, leading to control over object virtual tables or function pointers.

Exploitation requires user interaction, typically opening a malicious PDF either directly in Chrome or through an embedded <embed> or <iframe> element on an attacker-controlled web page. Successful exploitation yields code execution constrained by the Chrome sandbox. Attackers commonly chain this primitive with a separate sandbox escape to achieve full system compromise.

Root Cause

The root cause is improper object lifetime management within PDFium's parsing or rendering routines [CWE-416]. Specific technical details have not been published; Google withholds Chromium bug reports until a majority of users have updated. The corresponding Chromium Issue Tracker entry remains restricted.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker hosts or delivers a crafted PDF document. When the victim opens the PDF in a vulnerable Chrome instance, the parser triggers the use-after-free condition. No authentication is required, and the attack scales easily through phishing, drive-by downloads, or malicious advertisements.

No verified public proof-of-concept has been released. Refer to the Google Chrome Desktop Update for vendor commentary.

Detection Methods for CVE-2026-11303

Indicators of Compromise

Chrome renderer process crashes referencing pdfium.dll, libpdfium.so, or PDFium frames in stack traces
Unexpected child processes spawned from chrome.exe immediately after a PDF is opened
Outbound connections from a Chrome renderer to uncategorized or newly registered domains following PDF rendering
PDF files delivered via email or download with embedded JavaScript actions or unusually large object streams

Detection Strategies

Inspect endpoint telemetry for browser renderer crashes correlated with PDF MIME type handling
Hunt for anomalous module loads or memory allocations inside Chrome renderer processes
Apply YARA or content rules against inbound PDFs to flag malformed cross-reference tables and crafted object streams
Correlate web proxy logs with endpoint process events to identify users who fetched a malicious PDF before a crash

Monitoring Recommendations

Track Chrome version inventory across managed endpoints and alert on builds below 149.0.7827.53
Forward Chrome crash reports and renderer telemetry to a centralized data lake for hunting
Monitor for post-exploitation behavior such as credential access, token theft, or persistence following Chrome activity

How to Mitigate CVE-2026-11303

Immediate Actions Required

Update Google Chrome to version 149.0.7827.53 or later on all Windows, macOS, and Linux endpoints
Restart Chrome after updating to ensure the patched binary is loaded
Verify enterprise update policies are not blocking or delaying Chrome stable channel updates
Audit Chromium-based browsers and embedded WebViews that share the PDFium codebase

Patch Information

Google released the fix in the Chrome Stable channel build 149.0.7827.53. Details are published in the Stable Channel Update for Desktop. Administrators using Group Policy, Jamf, or Linux package managers should confirm rollout completion through their management console.

Workarounds

Disable Chrome's built-in PDF viewer through the AlwaysOpenPdfExternally enterprise policy until patching completes
Route inbound PDF attachments through a sandboxed conversion or detonation gateway
Restrict execution of Chrome to managed user contexts and block opening of PDFs from untrusted sources via browser policy

bash

# Example Chrome enterprise policy to force external PDF handling on Windows
reg add "HKLM\Software\Policies\Google\Chrome" /v AlwaysOpenPdfExternally /t REG_DWORD /d 1 /f

# Verify installed Chrome version on Linux
google-chrome --version

# Verify installed Chrome version on macOS
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --version