CVE-2017-12173 in sssd
Summary
by MITRE
It was found that sssd's sysdb_search_user_by_upn_res() function before 1.16.0 did not sanitize requests when querying its local cache and was vulnerable to injection. In a centralized login environment, if a password hash was locally cached for a given user, an authenticated attacker could use this flaw to retrieve it.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2017-12173 resides within the sssd (System Security Services Daemon) component of Red Hat Enterprise Linux and similar distributions. This flaw affects versions prior to 1.16.0 and specifically targets the sysdb_search_user_by_upn_res() function which handles user authentication queries in centralized login environments. The issue manifests as a failure to properly sanitize input parameters during cache queries, creating a path for malicious exploitation. The vulnerability operates within the context of directory services where sssd manages authentication against various backends including Active Directory, LDAP, and other directory services. When users authenticate through these systems, sssd maintains local caches of user information including password hashes for performance optimization. The improper sanitization occurs during the processing of User Principal Name (UPN) queries which are commonly used in Active Directory environments to uniquely identify users.
The technical flaw represents a classic injection vulnerability where untrusted input flows directly into the local cache query mechanism without proper validation or sanitization. When an authenticated attacker submits a specially crafted UPN query, the function fails to properly escape or validate the input before using it in internal cache operations. This allows the attacker to manipulate the cache query structure and potentially extract sensitive information stored in the local database. The vulnerability is particularly dangerous because it operates at the system level within the authentication daemon itself, rather than through network protocols or user-facing interfaces. The attack vector requires authentication to the system, but once achieved, the attacker can leverage this flaw to access cached password hashes that would normally be protected by proper access controls. This weakness directly relates to CWE-77 and CWE-94, which categorize injection vulnerabilities and improper input sanitization respectively.
The operational impact of this vulnerability extends beyond simple information disclosure, as it compromises the integrity of the authentication caching mechanism in centralized environments. In enterprise settings where sssd is commonly deployed, an attacker with access to a system could potentially retrieve cached password hashes for multiple users, enabling offline password cracking attacks or facilitating further lateral movement within the network. The vulnerability is particularly concerning in environments where users authenticate through Active Directory integration, as the cached credentials often include more than just password hashes but may contain additional authentication tokens or session information. This flaw undermines the security assumptions of the local cache mechanism which is designed to provide performance benefits while maintaining security boundaries. The attack could lead to privilege escalation, account takeover, and broader compromise of the authentication infrastructure, especially when combined with other vulnerabilities or attack techniques. Organizations relying on sssd for centralized authentication face significant risk if this vulnerability remains unpatched.
Mitigation strategies for CVE-2017-12173 primarily involve immediate deployment of patches and updates to sssd versions 1.16.0 or later where the sanitization issue has been addressed. System administrators should conduct comprehensive vulnerability assessments to identify all systems running affected sssd versions and prioritize patching according to risk assessment. Additional defensive measures include implementing network segmentation to limit access to systems running sssd, monitoring for unusual authentication patterns or cache query activities, and ensuring that local cache files have appropriate file system permissions to prevent unauthorized access. Organizations should also review their authentication policies and consider implementing additional authentication layers such as multi-factor authentication to reduce the impact of credential compromise. The remediation process should include thorough testing of patches in non-production environments to ensure compatibility with existing authentication configurations. Security teams should monitor for exploitation attempts through intrusion detection systems and review system logs for evidence of cache query manipulation or unauthorized access to authentication caches. This vulnerability aligns with ATT&CK technique T1550.001 for use of valid accounts and T1078 for valid accounts, demonstrating how local authentication cache vulnerabilities can be leveraged for broader system compromise.