CVE-2026-121179 in Chrome
Summary
by MITRE • 11/03/2026
Use after free 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 HTML page. (Chromium security severity: High)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified as a use-after-free flaw within PDFium, the component responsible for rendering Portable Document Format files in Google Chrome prior to version 157.0.8103.38, represents a critical memory management error that can be leveraged by remote attackers to achieve arbitrary code execution. This specific class of vulnerability occurs when an application continues to use a pointer after the memory it points to has been freed and potentially reallocated for other purposes. In the context of PDFium, this flaw likely stems from improper handling of object lifecycles during the parsing or rendering of complex PDF structures embedded within HTML pages. When a crafted HTML page containing maliciously constructed PDF content is loaded by an affected browser instance, the renderer may release memory associated with certain internal objects while retaining references to those same objects elsewhere in the execution flow.
From a technical perspective, this use-after-free condition allows an attacker to manipulate the heap state of the browser process. By carefully crafting the input data, specifically within the HTML page that triggers the PDF rendering engine, an adversary can control what data is written into the freed memory region before it is accessed again. This scenario creates opportunities for heap spraying or targeted overwrites, which are fundamental techniques in exploitation chains designed to gain control over program execution flow. The attacker's goal is typically to overwrite function pointers or virtual table entries within these reused objects, thereby redirecting code execution to shellcode injected into the process memory space.
The operational impact of this vulnerability is severe due to its potential for remote code execution via a web page. Although Google Chrome employs sandboxing mechanisms designed to isolate browser processes and limit the damage caused by successful exploits, use-after-free vulnerabilities in core rendering components like PDFium have historically proven difficult to fully mitigate through sandboxing alone if the exploit chain includes additional primitives such as arbitrary read or write capabilities. The Chromium security severity rating of High reflects the likelihood that this flaw can be successfully exploited to escape the browser's isolation boundaries and execute code with the privileges of the user running the application. This could lead to full system compromise, data theft, or installation of persistent malware on the victim's device without any further interaction beyond visiting a malicious website.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-416, which describes use after free errors resulting from improper memory management practices. In terms of offensive security frameworks, this exploit scenario maps to MITRE ATT&CK techniques related to initial access and privilege escalation within the browser environment. Specifically, it relates to tactics involving exploitation for client-side code execution where attackers leverage vulnerabilities in web browsers or their components to gain a foothold on target systems. The reliance on HTML pages as the delivery mechanism highlights the importance of content validation and input sanitization at the application layer, although modern defenses primarily rely on memory safety features and sandboxing rather than purely preventive coding practices for such complex rendering engines.
Mitigation strategies focus heavily on timely patch management and defense-in-depth measures. Users must update Google Chrome to version 157.0.8103.38 or later immediately upon availability, as this release contains the necessary code fixes that ensure proper memory deallocation and reference counting within PDFium. Beyond updating software, organizations should enforce strict browser security policies, including disabling unnecessary plugins and restricting script execution on untrusted sites where possible. Additionally, enabling advanced sandboxing features such as Site Isolation can help contain potential breaches by ensuring that each tab runs in its own process with distinct memory spaces, thereby reducing the effectiveness of heap-based exploitation techniques even if a vulnerability is present. Regular security awareness training for users to avoid visiting suspicious websites remains a critical complementary control against social engineering vectors often used to deliver such crafted HTML pages.