CVE-2006-0056 in PAM-MySQL
Summary
by MITRE
Double free vulnerability in the authentication and authentication token alteration code in PAM-MySQL 0.6.x before 0.6.2 and 0.7.x before 0.7pre3 allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via crafted passwords, which lead to a double free of a pointer that was created by the pam_get_item function. NOTE: this issue only occurs in certain configurations in which there are multiple PAM modules, PAM-MySQL is not evaluated first, and there are no requisite modules before PAM-MySQL.
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Analysis
by VulDB Data Team • 07/21/2024
The vulnerability described in CVE-2006-0056 represents a critical double free error within the PAM-MySQL authentication module that can lead to both denial of service and potential arbitrary code execution. This issue affects versions 0.6.x prior to 0.6.2 and 0.7.x prior to 0.7pre3, making it a significant concern for systems utilizing this particular PAM module for MySQL authentication. The vulnerability stems from improper memory management within the authentication and authentication token alteration code paths, specifically when handling crafted password inputs that trigger the double free condition.
The technical flaw manifests when a pointer allocated by the pam_get_item function undergoes a double free operation due to flawed memory management logic in the authentication processing code. This occurs during the handling of authentication tokens where the same memory location gets freed twice, creating a classic heap corruption scenario. The double free vulnerability is classified under CWE-415 as an attempt to free memory a second time, which can result in memory corruption and potentially allow attackers to execute arbitrary code. The condition requires specific environmental configurations to be exploitable, including the presence of multiple PAM modules where PAM-MySQL is not evaluated first, and the absence of requisite modules positioned before PAM-MySQL in the module stack.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution, making it particularly dangerous in networked environments. When exploited, the double free condition can cause application crashes and potentially allow attackers to manipulate the heap structure to execute malicious code with the privileges of the affected service. This vulnerability aligns with ATT&CK technique T1068 which covers 'Exploitation for Privilege Escalation' and T1190 which covers 'Exploitation of Remote Services'. The attack vector requires remote access through crafted password inputs that specifically trigger the vulnerable code path, making it particularly insidious as it can be exploited through normal authentication attempts.
Mitigation strategies should focus on immediate patching to versions 0.6.2 or 0.7pre3 and later, which contain the necessary memory management fixes. System administrators should also implement proper PAM module ordering to ensure PAM-MySQL is evaluated first in the authentication stack, thereby preventing the vulnerable code path from being triggered. Additionally, monitoring for unusual authentication patterns and implementing proper input validation can help detect potential exploitation attempts. The vulnerability highlights the importance of proper memory management in security-critical components and demonstrates how seemingly benign authentication flows can contain critical heap corruption vulnerabilities. Organizations should also consider implementing additional security controls such as authentication rate limiting and monitoring for authentication failures that might indicate exploitation attempts.