CVE-2026-90463 in Red Hat
Summary
by MITRE • 09/14/2026
A flaw was found in the sssd NSS responder. This input validation vulnerability allows a local attacker, by sending specially crafted service lookup requests to the NSS responder's UNIX socket, to cause an out-of-bounds read. This out-of-bounds read may lead to a denial of service (DoS) by crashing the NSS responder process. While unprivileged local clients can typically reach the socket, there is no evidence of privilege escalation or reliable data disclosure.
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Analysis
by VulDB Data Team • 09/14/2026
The System Security Services Daemon (SSSD) serves as a critical component in modern Linux and Unix environments, acting as an intermediary between the operating system's Name Service Switch infrastructure and various identity providers such as Active Directory, LDAP, or Kerberos realms. Within this architecture, the NSS responder module is responsible for handling requests from local applications that need to resolve user identities, group memberships, and other account-related information. A significant vulnerability has been identified within this specific component, classified as an input validation flaw that manifests as a buffer over-read condition. This defect arises when the SSSD NSS responder processes service lookup requests sent via its UNIX socket interface without adequately verifying the bounds of the provided data structures or string lengths before reading from memory buffers.
The technical nature of this vulnerability centers on improper boundary checks during the parsing and processing of incoming network-style packets, albeit transmitted over a local IPC mechanism. When an attacker sends specially crafted service lookup requests to the NSS responder's UNIX socket, the application fails to ensure that the requested data length does not exceed the allocated buffer size or valid memory regions associated with the request context. Consequently, this leads to an out-of-bounds read operation where the process attempts to access memory locations beyond its intended allocation boundaries. While modern operating systems employ protections such as Address Space Layout Randomization (ASLR) and non-executable stacks that mitigate many exploitation vectors for over-reads, the immediate consequence of accessing invalid memory is often a segmentation fault or similar critical error within the responder process itself.
From an operational perspective, this vulnerability primarily facilitates a denial-of-service attack against local services rather than providing direct access to sensitive data or system privileges. Because the SSSD NSS responder runs as root and handles requests from unprivileged local clients, any user account on the affected system can potentially trigger this crash by sending malformed lookup queries through the UNIX socket. The successful exploitation results in the termination of the NSS responder process, which disrupts identity resolution for all services relying on it. This disruption can cause applications that depend on real-time authentication or authorization checks to hang, fail, or behave unpredictably until the SSSD service is restarted by an administrator. Although there is currently no evidence suggesting that this flaw allows for privilege escalation or reliable data disclosure of sensitive information such as passwords or cryptographic keys, the availability impact remains severe in environments where continuous identity resolution is critical for system stability and user access control.
In terms of threat modeling and industry standards, this vulnerability aligns with CWE-125, which describes Out-of-bounds Read vulnerabilities resulting from insufficient validation of input data lengths relative to buffer capacities. Furthermore, the exploitation vector corresponds to ATT&CK technique T1078, specifically involving valid accounts used for local persistence or disruption, as it requires a local authenticated user to interact with the system service. The attack surface is limited by the requirement that the attacker must have access to the UNIX socket associated with SSSD, which typically restricts exploitation to users who already possess some level of shell access on the host machine. This limitation significantly reduces the risk profile compared to remote code execution vulnerabilities but maintains a high severity due to the potential for service disruption in production environments.
Mitigation strategies should focus primarily on applying vendor-provided patches that update the SSSD package to versions where input validation logic has been hardened to enforce strict buffer boundaries during request processing. System administrators must ensure that automatic security updates are enabled or manually apply these fixes as soon as they become available from their respective distribution maintainers. In addition to patching, organizations should implement monitoring solutions capable of detecting abnormal termination patterns in the SSSD NSS responder process, which could indicate ongoing exploitation attempts by malicious insiders or compromised accounts. Restricting access to critical system services through strict file permissions on UNIX sockets and employing least-privilege principles for user accounts can further reduce the attack surface, although these measures do not replace the need for timely software updates addressing this specific input validation flaw.