CVE-2026-104046 in Red Hat
Summary
by MITRE • 10/07/2026
A flaw was found in SSSD (System Security Services Daemon). When Identity Provider (IdP) authentication is enabled, pre-authentication requests retain state in memory without being cleared or timed out. A local attacker can repeatedly initiate authentication flows without completing them, causing unbounded memory consumption. This memory exhaustion can lead to a Denial of Service (DoS) by degrading or terminating SSSD authentication services.
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Analysis
by VulDB Data Team • 10/07/2026
The System Security Services Daemon serves as a critical component in Linux and Unix environments for managing access to remote directories and authentication mechanisms, particularly when integrated with Identity Providers such as Active Directory or FreeIPA. The identified vulnerability resides within the handling of pre-authentication requests when IdP authentication is enabled. Under normal operational conditions, these daemon processes are expected to manage state transitions efficiently, ensuring that temporary data associated with incomplete or abandoned authentication sessions is properly cleaned up from memory once a session concludes or times out according to configured policies. However, in this specific scenario, the implementation fails to clear or timeout pre-authentication request states after they have been initiated by a client. This oversight means that every time an identity provider connection attempt begins but does not reach completion, the associated state information remains allocated in the daemon's memory space indefinitely rather than being released back to the system pool for reuse or garbage collection.
This architectural flaw creates a direct pathway for resource exhaustion attacks targeting local users on the affected system. Because SSSD typically runs with elevated privileges to facilitate secure authentication and identity resolution, an unprivileged local attacker can exploit this behavior by repeatedly initiating authentication flows without completing them. Each incomplete request consumes additional memory resources within the SSSD process. Since there is no mechanism to automatically purge these stale states or enforce a maximum age for such pending requests, the memory consumption grows linearly with each new attempt. Over time, particularly in environments where high volumes of connection attempts occur, this unbounded growth can consume all available system memory allocated to the daemon or even exhaust physical RAM if limits are not strictly enforced by cgroups or other containerization tools.
The operational impact of this vulnerability is primarily a Denial of Service against authentication services and potentially broader system stability. As SSSD consumes increasing amounts of memory, it may trigger out-of-memory conditions that cause the process to crash or be terminated by the operating system's kernel oom-killer. When SSSD fails, local users lose their ability to authenticate via network-based identity sources, effectively locking them out of systems that rely on this daemon for login credentials and group membership resolution. In severe cases where memory pressure becomes extreme across the entire host due to multiple affected services or insufficient isolation, system-wide instability can occur, affecting unrelated applications running on the same infrastructure. This represents a significant availability risk in enterprise environments where consistent access control is paramount.
From a classification perspective, this vulnerability aligns with CWE-400, which describes Uncontrolled Resource Consumption, specifically manifesting as memory exhaustion due to improper cleanup of transient state data. It also relates to CWE-770, Allocation of Resources Without Limits or Throttling, as the daemon does not impose constraints on the number of concurrent incomplete authentication states it will retain in memory. In terms of adversarial tactics, this flaw supports techniques associated with resource exhaustion within the MITRE ATT&CK framework, allowing an attacker to degrade service availability without necessarily gaining unauthorized access to data or executing arbitrary code. The attack vector is local, requiring physical or shell-level access to initiate the repeated connection attempts that trigger the memory leak.
Mitigation strategies should focus on both immediate remediation and long-term architectural improvements. Administrators are advised to apply vendor-provided patches as soon as they become available, which typically include fixes for state management logic in SSSD versions affected by this flaw. In environments where patching is delayed or not immediately feasible, operational mitigations can be implemented at the system level. Configuring memory limits using Linux cgroups for the sssd service process can prevent it from consuming excessive resources and crashing other critical services during an attack. Additionally, monitoring tools should be configured to alert on unusual spikes in SSSD memory usage or high rates of authentication failures, which may indicate active exploitation attempts. Ensuring that IdP configurations include appropriate timeout settings for connection retries might also help reduce the window of opportunity for attackers to accumulate state entries, although relying solely on configuration timeouts is insufficient given the fundamental flaw in cleanup logic.