CVE-2011-1144 in PEAR
Summary
by MITRE
The installer in PEAR 1.9.2 and earlier 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. NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-1072.
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Analysis
by VulDB Data Team • 10/18/2021
The vulnerability identified as CVE-2011-1144 represents a critical file overwrite flaw within the PEAR package management system affecting versions 1.9.2 and earlier. This security weakness specifically targets the installer component of PEAR, which is widely used for managing php packages and dependencies in web applications. The vulnerability stems from insufficient protection mechanisms during package installation processes, creating opportunities for malicious local users to manipulate the system through symbolic link attacks. The flaw is particularly concerning because it allows attackers to overwrite arbitrary files on the target system, potentially leading to privilege escalation or complete system compromise. This vulnerability directly impacts the integrity of the package installation process and represents a significant threat to systems relying on PEAR for php package management.
The technical implementation of this vulnerability involves the exploitation of directory traversal and symbolic link manipulation within the PEAR installer's handling of temporary files and directories. When PEAR processes package installations, it creates temporary files in specific directories including download_dir, cache_dir, tmp_dir, and pear-build-download. The installer fails to properly validate symbolic links before processing these temporary files, allowing an attacker to create malicious symbolic links that point to critical system files. When the installer attempts to write to these directories, it follows the symbolic links and overwrites the target files rather than the intended temporary files. This type of attack pattern is categorized under CWE-59 as improper link resolution without maximum restrictiveness, and specifically relates to CWE-22 which deals with path traversal vulnerabilities. The flaw demonstrates a classic example of insufficient input validation and improper privilege handling during file operations.
The operational impact of CVE-2011-1144 extends beyond simple file overwrites to potentially enable more sophisticated attacks within compromised systems. Local users who can manipulate the installation environment gain the ability to overwrite critical system files, configuration files, or even executables, which could lead to privilege escalation or persistent backdoors. The vulnerability affects the fundamental trust model of package installation, as it undermines the security assumptions that legitimate package installations should be safe from local interference. Attackers could potentially overwrite system binaries, configuration files, or log files to maintain persistence or hide their activities. This vulnerability also impacts the integrity of the software supply chain, as compromised packages could be used to distribute malicious code to multiple systems. The attack vector requires local system access but does not require network connectivity, making it particularly dangerous in multi-user environments or shared hosting scenarios. The vulnerability's persistence across multiple directories (download_dir, cache_dir, tmp_dir, and pear-build-download) increases the attack surface and makes comprehensive mitigation more challenging.
The remediation for CVE-2011-1144 requires immediate patching of PEAR installations to versions 1.9.3 or later, which contain the proper fix for this vulnerability. Organizations should also implement additional security measures including restricting write permissions on critical directories, monitoring for unauthorized symbolic link creation, and conducting regular security audits of package management systems. System administrators should consider implementing file integrity monitoring solutions to detect unauthorized file modifications in package directories. The fix addresses the root cause by ensuring that symbolic links are properly resolved and validated before file operations occur, preventing the exploitation of directory traversal weaknesses. Security best practices should include regular updates of package management tools, implementation of least privilege principles for package installation processes, and maintaining secure configuration practices for temporary directories. This vulnerability also highlights the importance of proper input validation and secure file handling practices, aligning with ATT&CK technique T1059.007 for command and scripting interpreter and T1548.001 for abuse of privileges. Organizations should also consider implementing application whitelisting and mandatory access controls to further protect against similar vulnerabilities in package management systems.