CVE-2026-104032 in sssd
Summary
by MITRE • 10/06/2026
A flaw was found in SSSD. An unprivileged local user can repeatedly request master automount map updates through the autofs responder due to missing authorization checks. This triggers global cache invalidation and forces repeated lookups to backend directory providers, leading to a Denial of Service (DoS) from degraded automount availability and elevated resource consumption.
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Analysis
by VulDB Data Team • 10/06/2026
The Security-Enhanced Linux System Daemon, commonly known as SSSD, serves as a critical component in enterprise identity management infrastructure by providing access control information for remote users and systems to local services such as login, name service switch, and automounting. Within this architecture, the autofs responder plays a pivotal role in managing dynamic filesystem mounts based on maps retrieved from directory providers like LDAP or Active Directory. A significant security flaw has been identified within the authorization logic governing these requests, specifically affecting unprivileged local users who interact with the system through standard user accounts rather than administrative privileges. This vulnerability stems from missing access control checks that should validate whether a requesting process is authorized to trigger master automount map updates via the autofs responder interface.
The technical nature of this flaw involves an improper implementation of authorization boundaries within the SSSD daemon's communication channels, typically D-Bus or similar IPC mechanisms used for inter-process communication. When an unprivileged user issues repeated requests for master automount map updates, the system fails to verify if such actions are permitted under current security policies. Consequently, each request is processed by the backend directory provider without adequate restriction. This lack of validation allows any local user with shell access to initiate a high volume of lookups against potentially resource-intensive remote directories. The operational impact manifests as a severe Denial of Service condition where the automount service becomes degraded due to constant cache invalidation and subsequent forced re-lookups.
From an infrastructure perspective, this vulnerability leads to elevated resource consumption on both the local host and the backend directory servers. The repeated global cache invalidations force SSSD to discard cached entries and request fresh data from the identity provider repeatedly. This not only consumes significant CPU and memory resources locally but also generates excessive network traffic and query loads against the central authentication infrastructure, potentially impacting other services relying on the same directory providers. In environments where automounting is heavily utilized for accessing home directories or shared storage, this degradation can result in users being unable to mount necessary filesystems effectively, thereby disrupting productivity and operational continuity.
This vulnerability aligns with CWE-284, which describes Improper Access Control, as it involves a failure to enforce proper authorization checks before allowing an action that impacts system stability. Furthermore, the exploitation pattern corresponds to ATT&CK technique T1059, specifically Command and Scripting Interpreter abuse or potentially T1496 if considered part of resource hijacking for denial of service purposes, although primarily it represents a local privilege escalation vector leading to availability compromise rather than direct command execution by an attacker. The scenario highlights the risks associated with overly permissive default configurations in identity management daemons where local users are granted excessive capabilities over system-level services without sufficient scrutiny.
Mitigation strategies must focus on tightening access controls within SSSD configuration and applying available patches that address this specific authorization gap. Administrators should ensure that their systems are updated to versions of SSSD that include fixes for these missing checks, thereby restricting the ability of unprivileged users to trigger master map updates arbitrarily. Additionally, implementing rate limiting mechanisms at the network or service level can help mitigate the impact by throttling excessive requests from any single source. It is also advisable to review and harden automount configurations to minimize reliance on frequent dynamic lookups where possible, reducing the attack surface for such denial-of-service vectors while maintaining necessary functionality for legitimate users.