CVE-2015-8949 in DBD::mysql
Summary
by MITRE
Use-after-free vulnerability in the my_login function in DBD::mysql before 4.033_01 allows attackers to have unspecified impact by leveraging a call to mysql_errno after a failure of my_login.
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Analysis
by VulDB Data Team • 09/14/2022
The CVE-2015-8949 vulnerability represents a critical use-after-free flaw within the DBD::mysql Perl database driver library, specifically affecting versions prior to 4.033_01. This vulnerability resides in the my_login function which handles the authentication process when connecting to MySQL databases through Perl applications. The flaw occurs when the mysql_errno function is invoked after a failed my_login operation, creating a scenario where freed memory locations are accessed, potentially leading to arbitrary code execution or system compromise. The vulnerability demonstrates a classic memory safety issue that has been documented under CWE-416, which specifically addresses use-after-free conditions in software implementations.
The technical exploitation of this vulnerability requires an attacker to trigger a failure within the my_login function while simultaneously invoking mysql_errno to access memory that has already been freed. This sequence creates a race condition where the memory management system has already deallocated the relevant structures, but the subsequent mysql_errno call attempts to reference them. The impact of this vulnerability can be severe as it allows attackers to potentially execute arbitrary code with the privileges of the affected application process, which typically runs with database access permissions. The unspecified impact mentioned in the CVE description reflects the potential for various malicious outcomes including privilege escalation, data exfiltration, or complete system compromise depending on the execution environment and application configuration.
From an operational standpoint, this vulnerability affects any Perl application utilizing the DBD::mysql driver for MySQL database connections, particularly those that may not properly handle connection failures or error conditions. The attack vector typically involves crafting malicious database connection parameters or exploiting specific error handling paths that lead to the vulnerable code path. Organizations running web applications, database management tools, or any Perl-based systems that interface with MySQL databases are at risk. The vulnerability aligns with ATT&CK technique T1059.007 for remote code execution through application vulnerabilities and represents a significant concern for systems where database credentials are exposed to untrusted inputs.
Mitigation strategies for CVE-2015-8949 focus primarily on upgrading to DBD::mysql version 4.033_01 or later, which contains the necessary memory management fixes to prevent the use-after-free condition. System administrators should also implement proper input validation and error handling practices in their Perl applications to minimize exposure, though the primary fix must come from updating the vulnerable library. Additionally, organizations should consider implementing network segmentation and access controls to limit the potential impact of successful exploitation, while monitoring for anomalous database connection patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the importance of maintaining up-to-date database driver libraries and the critical nature of memory safety in database connectivity components.