CVE-2002-0030 in Acrobat Reader
Summary
by MITRE
The digital signature mechanism for the Adobe Acrobat PDF viewer only verifies the PE header of executable code for a plug-in, which can allow attackers to execute arbitrary code in certified mode by making the plug-in appear to be signed by Adobe.
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Analysis
by VulDB Data Team • 06/16/2024
The vulnerability described in CVE-2002-0030 represents a critical flaw in Adobe Acrobat PDF viewer's digital signature verification process that fundamentally undermines the security model designed to protect users from malicious content. This weakness specifically affects the verification mechanism used to validate plug-in executables within the PDF environment, creating a pathway for attackers to bypass security controls that were intended to ensure only trusted code could execute within the certified viewing mode. The vulnerability resides in the implementation of the signature verification logic rather than the signature itself, making it particularly insidious as it exploits a legitimate security feature to enable unauthorized execution.
The technical flaw manifests in the PDF viewer's approach to validating plug-in executables, where the digital signature verification process only examines the Portable Executable (PE) header of the executable code rather than performing a comprehensive integrity check of the entire file. This partial verification allows attackers to manipulate the PE header while keeping the actual malicious payload intact, effectively creating a false impression that the plug-in maintains Adobe's digital signature. The vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in signature verification mechanisms, specifically targeting the improper implementation of digital signature validation that fails to ensure complete file integrity. This approach to verification creates a false sense of security where the system accepts code as legitimate based on a partial signature check that can be easily manipulated.
The operational impact of this vulnerability is severe as it enables attackers to execute arbitrary code within the PDF viewer's certified mode, which is designed to provide a secure environment for viewing documents. When users encounter a PDF document containing a malicious plug-in, the viewer's incomplete signature verification allows the malicious code to appear as legitimate Adobe-signed software, bypassing the security controls that would normally prevent such execution. This vulnerability specifically affects the privilege escalation and code execution capabilities within the context of PDF viewing, allowing attackers to gain unauthorized access to system resources and potentially execute malicious payloads with the privileges of the user running the PDF viewer. The attack vector leverages the trust model inherent in digital signatures, where the system's reliance on partial verification creates a window of opportunity for exploitation.
The security implications extend beyond simple code execution to encompass a broader compromise of the PDF viewer's integrity protection mechanisms, as this flaw demonstrates how incomplete security implementations can create exploitable gaps in defense. Attackers can craft malicious plug-ins that maintain valid PE headers while containing malicious code, effectively subverting the digital signature verification process that should prevent such execution. This vulnerability relates to ATT&CK technique T1059.007 for command and scripting interpreter, as it enables the execution of arbitrary commands through the malicious plug-in mechanism, and T1550.003 for use of stolen credentials, as the compromised system may be used to escalate privileges or access additional resources. Organizations using Adobe Acrobat PDF viewers are particularly vulnerable to this attack, as the flaw exists in the core verification logic and requires a complete implementation update to address properly.
Mitigation strategies for this vulnerability require immediate patching of Adobe Acrobat PDF viewer installations to address the incomplete signature verification implementation, as well as implementing additional security measures such as application whitelisting and restricted execution environments. System administrators should disable or restrict the execution of plug-ins within PDF documents, particularly those from untrusted sources, and implement network-based controls to prevent the download and execution of potentially malicious plug-ins. The vulnerability highlights the importance of comprehensive cryptographic verification that examines entire file integrity rather than partial header validation, and organizations should ensure that all digital signature verification processes implement complete file integrity checks to prevent similar exploitation vectors. Regular security updates and thorough testing of security implementations are essential to prevent the exploitation of similar weaknesses in other security mechanisms.