CVE-2011-1072 in PEAR
Summary
by MITRE
The installer in PEAR before 1.9.2 allows local users to overwrite arbitrary files via a symlink attack on the package.xml file, related to the (1) download_dir, (2) cache_dir, (3) tmp_dir, and (4) pear-build-download directories, a different vulnerability than CVE-2007-2519.
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Analysis
by VulDB Data Team • 01/15/2025
The vulnerability identified as CVE-2011-1072 affects the PHP Extension and Application Repository (PEAR) installer version 1.9.1 and earlier, presenting a significant local privilege escalation risk through symbolic link manipulation. This flaw resides in the installer's handling of temporary file operations during package installation processes, specifically targeting four critical directory paths including download_dir, cache_dir, tmp_dir, and pear-build-download. The vulnerability enables malicious local users to overwrite arbitrary files on the system by exploiting a race condition in the installation process where symbolic links can be manipulated to redirect file operations to unintended destinations. The installer's failure to properly validate or secure these temporary directories creates an attack surface that allows adversaries to place malicious symbolic links in these locations, which are then followed during package installation, resulting in arbitrary file overwrite operations. This vulnerability represents a distinct issue from CVE-2007-2519, indicating a separate code path or implementation flaw within the PEAR installer's file handling mechanisms.
The technical exploitation of this vulnerability occurs through a carefully crafted symlink attack that leverages the installer's trust in temporary directory contents without proper verification. During package installation, PEAR creates temporary files in the specified directories and subsequently processes these files to generate the final package.xml structure. Attackers can create symbolic links in any of the four vulnerable directories before the installer processes them, causing the installer to follow these links and write content to arbitrary locations on the filesystem. The flaw stems from insufficient input validation and lack of proper file integrity checks in the installer's temporary file handling, allowing attackers to bypass normal access controls and potentially overwrite system-critical files with malicious content. This type of vulnerability aligns with CWE-59 and CWE-36, representing weaknesses in file path resolution and improper file access controls. The attack vector specifically maps to ATT&CK technique T1059.007 for execution through command-line interfaces and T1548.001 for privilege escalation through local system modifications.
The operational impact of CVE-2011-1072 extends beyond simple file overwrite capabilities, as it can enable attackers to compromise the integrity of the entire PHP application ecosystem on affected systems. Local attackers with minimal privileges can leverage this vulnerability to escalate their access level by overwriting critical system files, configuration files, or even the PEAR installer itself, potentially leading to complete system compromise. The vulnerability affects systems where PEAR is installed with default or user-specified temporary directories that are writable by unprivileged users, creating widespread exposure across various hosting environments and development systems. Organizations running multiple PHP applications that depend on PEAR for package management face elevated risk, as successful exploitation could allow attackers to modify core system components or inject malicious code into the PHP execution environment. The vulnerability's persistence across different temporary directory types indicates a fundamental flaw in the installer's design that requires careful consideration during system hardening and security configuration. This weakness demonstrates the critical importance of proper temporary file handling in package managers and the potential for privilege escalation through seemingly innocuous file operations.
Mitigation strategies for CVE-2011-1072 focus on both immediate patching and long-term system hardening approaches. The primary and most effective solution involves upgrading to PEAR version 1.9.2 or later, where the installer properly validates temporary file operations and implements secure file handling mechanisms. System administrators should also implement restrictive permissions on the vulnerable directories, ensuring that only authorized users can write to these locations and that symbolic links cannot be created or modified by unprivileged accounts. The implementation of proper file integrity checks and atomic file operations within the installer process can prevent the exploitation of race conditions that enable the symlink attack. Organizations should consider implementing additional security controls such as mandatory access controls, file system monitoring, and regular vulnerability assessments to detect potential exploitation attempts. Security hardening practices should include disabling unnecessary temporary directory access, implementing proper directory permissions, and regularly auditing system configurations to prevent the creation of vulnerable temporary file locations. The vulnerability highlights the importance of secure coding practices in package managers and the need for comprehensive security testing of file handling operations in software installation processes.