CVE-2026-104030 in sssd
Summary
by MITRE • 10/06/2026
A flaw was found in sssd. This vulnerability allows a local user to cause a Denial of Service (DoS) by submitting a specially crafted passkey authentication token that lacks null terminators. The authentication service reads past the end of the provided memory buffer, causing the process to crash and disrupting authentication services.
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Analysis
by VulDB Data Team • 10/06/2026
The identified vulnerability resides within the System Security Services Daemon, commonly known as SSSD, which is a critical component in Linux environments responsible for providing access to remote directory services and authentication mechanisms. This specific flaw manifests during the processing of passkey-based authentication tokens, particularly when these tokens are malformed or improperly formatted by local users. The core technical deficiency involves an improper handling of string termination characters within the memory buffer allocated for storing the authentication token data. Specifically, the software fails to verify that the provided passkey authentication token includes a null terminator at its end before proceeding with subsequent processing steps. This oversight represents a classic instance of CWE-126, or Buffer Over-read, where the application logic assumes valid string boundaries without performing adequate bounds checking on the input data structure.
When a local user submits a specially crafted passkey authentication token that lacks the required null terminator, the SSSD process attempts to read memory beyond the allocated buffer boundary in search of this terminating character. This out-of-bounds memory access leads to undefined behavior within the application runtime environment. In most practical scenarios involving C-based systems like SSSD, such an operation results in a segmentation fault or similar critical error that causes the authentication service process to crash abruptly. The operational impact is immediate and severe for any system relying on this specific instance of SSSD for user verification. By triggering this condition repeatedly or even once depending on memory layout, a local unprivileged user can disrupt the availability of authentication services effectively creating a Denial of Service scenario against other users attempting to log in or authenticate via networked directory services managed by that daemon.
From an attacker perspective, this vulnerability aligns with MITRE ATT&CK technique T1499, Endpoint Denial of Service, as it allows for the disruption of system availability through resource exhaustion or process termination rather than data exfiltration or privilege escalation. While the immediate impact is limited to service unavailability, such instability can mask other malicious activities or create windows of opportunity for further exploitation if combined with race conditions in authentication logic. The vulnerability highlights the importance of rigorous input validation and memory safety practices within identity management infrastructure components that handle sensitive credential data from potentially untrusted local sources.
Mitigation strategies should focus on both immediate remediation and long-term architectural improvements. Administrators must ensure that SSSD is updated to a version where this buffer over-read issue has been patched by the upstream developers, as vendor-specific patches typically include strict bounds checking for all string inputs received from authentication modules. Additionally, implementing defense-in-depth measures such as restricting local user privileges on systems running critical identity services can reduce the attack surface available to potential exploiters. System monitoring tools should be configured to detect abnormal process terminations or crashes within SSSD-related processes, allowing for rapid incident response when such events occur. Furthermore, developers and security engineers reviewing similar codebases should enforce strict adherence to secure coding standards that mandate explicit validation of string lengths and termination characters before any memory traversal operations are performed on user-supplied data structures.