CVE-2026-68744 in SSSD
Summary
by MITRE • 08/04/2026
A flaw was found in SSSD. The sss_nss_protocol_fill_initgr() function in the NSS responder pre-allocates reply space for all group entries but does not shrink the packet when groups are skipped, causing uninitialized heap bytes to be transmitted to the client. A local attacker can exploit this to disclose cached directory data and heap layout information from the sssd_nss process.
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Analysis
by VulDB Data Team • 08/04/2026
This vulnerability exists within the SSSD (System Security Services Daemon) component, specifically in the NSS (Name Service Switch) responder module where the sss_nss_protocol_fill_initgr() function handles group membership initialization. The flaw represents a classic heap memory management issue where pre-allocated buffer space is not properly adjusted when certain group entries are skipped during processing. When the NSS responder processes group information for user authentication, it initially allocates memory buffers based on the maximum possible number of group entries without accounting for cases where some groups may be filtered out or skipped due to various conditions such as access control restrictions or duplicate detection mechanisms.
The technical exploitation of this vulnerability occurs through a heap-based information disclosure mechanism that allows local attackers to read uninitialized memory contents from the sssd_nss process heap. This happens because the function pre-allocates reply packets with sufficient space for all potential group entries but fails to reduce the packet size when actual group entries are skipped during processing. The uninitialized heap bytes contain fragments of previously allocated memory including cached directory data, system configuration information, and potentially sensitive authentication tokens that were stored in the same memory regions. This creates a scenario where an attacker can systematically read through the heap memory to extract cached directory information, user credentials, or other confidential data that was previously stored in the sssd_nss process memory space.
The operational impact of this vulnerability is significant for systems relying on SSSD for centralized authentication and authorization services. Local attackers with minimal privileges can exploit this flaw to gain access to cached directory information including group memberships, user attributes, and potentially sensitive authentication data that should remain protected within the sssd processes. This disclosure could enable further attacks by providing attackers with information about user accounts, group hierarchies, and system configuration details that could be leveraged for privilege escalation or lateral movement within the network environment. The vulnerability is particularly concerning in enterprise environments where SSSD is commonly used to integrate systems with centralized directory services such as Active Directory or LDAP.
From a security standards perspective, this vulnerability maps to CWE-1280 which specifically addresses "Heap-based Buffer Overflow" and related heap management issues, while also aligning with ATT&CK technique T1087.001 for account discovery through information gathering activities. The flaw demonstrates poor memory management practices in the NSS responder module where buffer allocation and deallocation are not properly synchronized with the actual data being processed. Organizations should implement immediate mitigations including applying security patches from the SSSD maintainers, monitoring for unusual heap access patterns in sssd processes, and restricting local system access to reduce the attack surface. Additionally, system administrators should consider implementing memory protection mechanisms such as stack canaries or heap randomization techniques to make exploitation more difficult, while also reviewing directory service configurations to minimize the amount of sensitive data cached in memory.
This vulnerability highlights the critical importance of proper buffer management in security-sensitive components and demonstrates how seemingly minor implementation flaws can lead to significant information disclosure risks. The SSSD project's response should include thorough code review of similar functions within the NSS responder module, implementation of proper memory reallocation when entries are skipped, and enhanced testing procedures that specifically target heap memory behavior under various group membership scenarios. Regular security assessments of authentication infrastructure components remain essential for identifying and addressing similar vulnerabilities before they can be exploited by malicious actors in real-world environments.