CVE-2008-5843 in pdfjam
Summary
by MITRE
Multiple untrusted search path vulnerabilities in pdfjam allow local users to gain privileges via a Trojan horse program in (1) the current working directory or (2) /var/tmp, related to the (a) pdf90, (b) pdfjoin, and (c) pdfnup scripts.
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Analysis
by VulDB Data Team • 08/03/2021
The vulnerability identified as CVE-2008-5843 represents a critical privilege escalation issue affecting the pdfjam suite of tools, which are commonly used for manipulating pdf documents through command line interfaces. This vulnerability stems from insecure direct object references and improper path resolution mechanisms within the pdfjam scripts that process pdf files. The affected scripts including pdf90, pdfjoin, and pdfnup fail to properly validate or sanitize the execution environment, creating opportunities for local attackers to execute arbitrary code with elevated privileges. This flaw specifically impacts systems where these tools are installed with setuid permissions or where the execution context allows privilege escalation.
The technical implementation of this vulnerability relies on the principle of untrusted search path exploitation, where the pdfjam scripts do not properly resolve absolute paths for their dependencies or helper programs. When these scripts execute, they search for required binaries in the current working directory and system directories including /var/tmp, without implementing proper path validation or using absolute paths for critical executables. This behavior aligns with CWE-426, which describes the weakness of allowing untrusted search paths that can be manipulated by attackers to substitute malicious executables for legitimate ones. The vulnerability occurs because the scripts rely on the system PATH variable without explicitly defining or validating the execution environment, making them susceptible to path traversal attacks.
The operational impact of this vulnerability is significant for systems running pdfjam tools, particularly those in multi-user environments where local privilege escalation could lead to complete system compromise. Attackers can place malicious Trojan horse programs in either the current working directory or /var/tmp, which are both searched by the pdfjam scripts during execution. When these scripts execute with elevated privileges, the malicious programs are invoked with the same privileges as the pdfjam tools, allowing attackers to execute arbitrary code as the privileged user. This vulnerability directly maps to ATT&CK technique T1068, which covers privilege escalation through local exploits and path manipulation. Systems where pdfjam is installed with setuid permissions or where users have write access to the /var/tmp directory are particularly vulnerable to this attack vector.
Mitigation strategies for CVE-2008-5843 require immediate implementation of several security controls to prevent exploitation of the untrusted search path vulnerabilities. System administrators should first ensure that all pdfjam scripts are executed with the least privilege necessary and that the current working directory is not included in the system PATH for critical operations. The recommended approach involves modifying the scripts to use absolute paths for all helper programs and binaries, eliminating the reliance on the PATH variable for critical executables. Additionally, implementing proper file system permissions and access controls on the /var/tmp directory can prevent attackers from placing malicious executables in that location. Regular security audits should verify that pdfjam tools are not installed with unnecessary setuid permissions, and that the execution environment properly validates all input paths. The implementation of these controls directly addresses the underlying CWE-426 weakness and reduces the attack surface for path-based privilege escalation attacks as outlined in the ATT&CK framework. Organizations should also consider updating to newer versions of pdfjam that have addressed these path resolution issues or implementing sandboxing techniques to isolate the execution environment of these tools.