CVE-2026-9960: Integer overflow in PDFium in Google Chrome prior to 148

Synopsis

An integer overflow in PDFium, the PDF rendering library bundled with Google Chrome, allows a remote attacker who has already compromised the renderer process to execute arbitrary code inside the browser sandbox via a crafted font file. The vulnerability is reachable over the network but requires the attacker to have pre-compromised the renderer and to trick a user into interacting with malicious content; successful exploitation gives the attacker code execution within the sandbox. A patched-image rebuild at Chrome 148.0.7778.216 is available on HarborGuard for affected environments.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the victim over the network, delivering a crafted font file through a web page or other network-accessible content.

• AuthenticationNot required

  No account or credentials are needed; the attacker operates as an unauthenticated remote party.

• Victim interactionRequired

  A user must interact with attacker-controlled content, such as opening a malicious PDF or visiting a crafted page, for the exploit to trigger.

• Attack complexityDetail

  Attack complexity is high because the attacker must first have compromised the renderer process before this integer overflow can be leveraged, introducing a prerequisite step beyond the attacker's direct control.

Blast Radius

• The attacker executes arbitrary code inside the Chrome sandbox, gaining full control of the sandboxed renderer process.
• Confidential data processed within the renderer, including page content and in-memory credentials, is readable by the attacker.
• The attacker can modify data handled by the renderer process, enabling tampering with rendered content or in-process state.
• If combined with a sandbox-escape primitive, the attacker moves from the sandboxed renderer to the underlying host process.