CVE-2026-121113 in Chrome
Summary
by MITRE • 11/03/2026
Buffer overflow in PDFium in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to execute arbitrary code inside the sandbox via a crafted PDF file. (Chromium security severity: High)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified involves a critical buffer overflow flaw within PDFium, the open-source PDF rendering engine utilized by Google Chrome and other Chromium-based browsers prior to version 157.0.8103.38. This defect represents a significant security risk because it allows for arbitrary code execution with elevated privileges relative to the browser sandbox environment. The root cause lies in improper handling of memory allocation or bounds checking when processing specific structures within a maliciously crafted PDF file. When an attacker constructs a PDF document containing specially designed objects, such as malformed form fields, annotations, or embedded content streams, they can trigger an overflow condition that corrupts adjacent memory regions. This corruption enables the injection and execution of arbitrary machine code on the victim's system, effectively bypassing the intended isolation mechanisms provided by the browser sandbox.
From a technical perspective, this vulnerability is classified under CWE-120, which denotes Buffer Copy without Checking Size of Input. The exploitation vector relies heavily on social engineering or drive-by download tactics where a user visits a compromised website hosting the malicious PDF or receives it via email and opens it within Chrome. Once triggered, the overflow allows an attacker to overwrite critical memory structures such as return addresses or function pointers. By carefully crafting the payload, attackers can achieve control over the instruction pointer, leading to remote code execution. The severity is rated as High by Chromium security teams because successful exploitation grants the attacker a foothold inside the sandboxed process, which may allow for further privilege escalation depending on system configurations and other concurrent vulnerabilities present in the operating environment.
The operational impact of this vulnerability extends beyond simple data corruption or denial of service. Successful exploitation results in full remote code execution within the context of the browser process. While modern browsers employ multiple layers of defense including sandboxing, address space layout randomization (ASLR), and data execution prevention (DEP), a well-crafted exploit can bypass these controls to execute native code. This compromises the confidentiality, integrity, and availability of user data stored locally or accessed through active sessions. Attackers could potentially install malware, steal sensitive information such as credentials or financial data, or use the compromised machine as part of a botnet. The ability to escape the sandbox significantly increases the blast radius of the attack, transforming what might have been an isolated incident into a systemic compromise of the host system.
In terms of threat intelligence and behavioral analysis, this vulnerability aligns with MITRE ATT&CK technique T1203, which covers Exploitation for Client Execution. Attackers frequently leverage client-side software vulnerabilities like those in PDF renderers to deliver payloads that execute automatically upon file opening or rendering. The use of a crafted PDF is a common tactic observed in targeted campaigns and widespread malware distribution networks alike. Defenders should monitor for unusual network connections originating from browser processes, particularly after the viewing of recent documents, as this may indicate successful exploitation attempts. Additionally, endpoint detection systems should look for anomalies in memory usage patterns or unexpected child process creation by Chrome.exe following PDF interactions.
Mitigation strategies primarily focus on timely patching and defensive configuration measures. The most effective remediation is to update Google Chrome to version 157.0.8103.38 or later, which includes the necessary code fixes to validate input sizes and prevent buffer overflows in PDFium. Organizations should enforce automatic updates for all endpoints running Chromium-based browsers to ensure rapid deployment of security patches. In environments where immediate patching is not feasible, network-level controls such as web proxies can be configured to block access to untrusted domains hosting PDF files or to sanitize incoming documents before they reach the client machine. Furthermore, enabling strict Content Security Policies and disabling JavaScript execution in embedded viewers can reduce the attack surface by limiting the capabilities available to malicious content within the browser context.
Security awareness training remains a critical component of defense against such vulnerabilities. Users should be educated on the risks associated with opening PDF files from unknown or untrusted sources. Implementing application whitelisting policies that restrict the execution of unsigned binaries can also provide an additional layer of protection, preventing even successfully exploited code from running if it does not match known good signatures. Regular vulnerability scanning and penetration testing focused on client-side applications help identify outdated software versions before they are targeted by active exploits in the wild. Maintaining a robust incident response plan ensures that any suspected compromise due to such vulnerabilities can be contained and investigated promptly, minimizing potential damage to organizational assets and data integrity.