CVE-2026-88252 in Red Hat
Summary
by MITRE • 10/06/2026
A flaw was found in sssd. A local user can cause a Denial of Service (DoS) by exhausting the responder service's available file descriptors (system handles used for open connections). By opening and maintaining many concurrent connections to a responder socket while continuing to queue new connection attempts, an attacker can trigger an unthrottled retry loop. This condition leads to high CPU utilization and stalls the service, preventing legitimate identity and authentication requests from being processed.
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Analysis
by VulDB Data Team • 10/06/2026
The System Security Services Daemon (SSSD) serves as a critical component in Linux-based environments for managing access to remote directories and authentication mechanisms. It acts as an intermediary between local system services such as NSS and PAM and backend identity providers like Active Directory or LDAP servers. A significant vulnerability has been identified within the SSSD architecture, specifically affecting its responder service which handles incoming connection requests from local clients. This flaw allows a local user to trigger a Denial of Service condition by exploiting how the daemon manages file descriptors and retry logic for failed connections. The core technical issue lies in an unthrottled retry loop that occurs when a client opens numerous concurrent connections to a responder socket while simultaneously queuing new connection attempts. Because the system does not adequately limit or back off these retries, it leads to resource exhaustion rather than graceful degradation of service.
From a technical perspective, this vulnerability is classified under CWE-787 as an Out-of-bounds Write due to improper handling of file descriptor limits and potentially CWE-400 Resource Exhaustion if viewed through the lens of uncontrolled resource consumption. The attacker leverages local access privileges to open multiple sockets against the SSSD responder interface. By maintaining these connections while continuously initiating new ones, the system is forced into a state where it cannot properly manage its file descriptor table. This results in high CPU utilization as the daemon spins in an infinite or excessive retry loop attempting to process queued requests that are failing due to resource constraints. The operational impact of this flaw is severe for any environment relying on SSSD for identity management, as legitimate authentication and identity lookup requests from other users are stalled until the service recovers or is restarted manually.
In terms of threat modeling, this attack vector aligns with MITRE ATT&CK technique T1499 Endpoint Denial of Service, specifically under sub-techniques involving resource exhaustion via application layer attacks. The vulnerability requires local access, which places it in a lower initial privilege level but makes it exploitable by any user account on the system, including compromised service accounts or users with shell access. This expands the attack surface significantly compared to remote-only vulnerabilities. The lack of throttling mechanisms means that even low-privileged users can cause substantial disruption to critical infrastructure services without needing elevated privileges initially.
Mitigation strategies should focus on both immediate remediation and long-term architectural improvements. Organizations must apply vendor-provided patches as soon as they become available, ensuring that the SSSD package is updated to versions where this retry logic has been corrected with appropriate rate limiting or exponential backoff mechanisms. In environments where patching cannot be applied immediately, administrators should implement strict file descriptor limits for the sssd process using operating system tools such as ulimit or systemd resource controls. Additionally, network segmentation and access control lists can restrict which local users are permitted to interact directly with SSSD responder sockets if possible through PAM configuration adjustments. Regular auditing of open connections and monitoring CPU usage spikes related to identity services can also help in early detection of such abuse attempts before they lead to full service outages.