CVE-2018-6072 in Chrome
Summary
by MITRE
An integer overflow leading to use after free in PDFium in Google Chrome prior to 65.0.3325.146 allowed a remote attacker to potentially exploit heap corruption via a crafted PDF file.
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Analysis
by VulDB Data Team • 06/06/2023
The vulnerability identified as CVE-2018-6072 represents a critical security flaw in PDFium, the PDF rendering engine used by Google Chrome and other applications. This integer overflow condition occurs within the memory management subsystem of PDFium, specifically when processing malformed PDF files that contain crafted integer values. The flaw manifests when the application attempts to allocate memory based on calculated integer values that exceed the maximum representable value for the data type, causing an integer overflow that subsequently leads to improper memory handling. The vulnerability is particularly dangerous because it can be triggered through remote exploitation via maliciously crafted PDF documents, making it a significant threat vector for attackers seeking to compromise user systems.
The technical implementation of this vulnerability involves a specific sequence of operations where PDFium processes PDF objects containing oversized integer values in their structure definitions. When these values overflow during arithmetic operations, they create invalid memory allocation sizes that the application subsequently uses to allocate heap memory. The improper handling of these overflow conditions results in memory being allocated and then freed, but the application continues to reference this freed memory location, creating a use-after-free condition. This condition allows attackers to manipulate heap memory layout and potentially execute arbitrary code with the privileges of the user running the vulnerable browser. The flaw is categorized under CWE-190 as an integer overflow condition, specifically involving signed integer overflow that leads to memory corruption.
The operational impact of CVE-2018-6072 extends beyond simple exploitation capabilities, as it enables sophisticated attack vectors that align with the techniques documented in the ATT&CK framework under the T1059.007 sub-technique for command and script interpreter. Attackers can leverage this vulnerability to execute code remotely through web-based attacks, potentially compromising user systems without requiring local access or physical presence. The vulnerability affects all versions of Google Chrome prior to 65.0.3325.146, making it particularly concerning given the widespread adoption of Chrome as a primary web browser. The heap corruption resulting from this flaw can be exploited to achieve privilege escalation, information disclosure, or system compromise, depending on the specific attack implementation and target environment. Organizations using affected versions face significant risk of successful exploitation through phishing campaigns or malicious websites that deliver crafted PDF files.
Mitigation strategies for CVE-2018-6072 primarily focus on immediate patching and system hardening measures. The most effective remediation involves upgrading to Google Chrome version 65.0.3325.146 or later, which includes the necessary fixes to prevent the integer overflow and subsequent use-after-free conditions. Additionally, organizations should implement browser security controls such as sandboxing, content security policies, and restricted browsing environments to minimize potential impact even if exploitation occurs. Network-level protections including web application firewalls and PDF content filtering can provide additional defense-in-depth layers. Security teams should also monitor for indicators of compromise related to this vulnerability and implement proper incident response procedures. The fix implemented by Google addresses the root cause by adding proper integer overflow checks and validation before memory allocation operations, preventing the creation of invalid memory allocation sizes that lead to heap corruption. This vulnerability highlights the importance of proper input validation and memory management practices in security-critical components, particularly those handling untrusted data such as PDF documents.