CVE-2026-89098 in Red Hat
Summary
by MITRE • 10/16/2026
A flaw was found in nfs-utils. The fsidd daemon improperly handles input received over its local domain socket by relying on program assertions to verify command arguments. A local user can exploit this vulnerability by sending a malformed request lacking the required arguments to trigger an assertion failure. This causes the daemon to crash, resulting in a Denial of Service (DoS) for filesystem identifier lookup services until restarted.
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Analysis
by VulDB Data Team • 10/16/2026
The nfs-utils package provides essential utilities for managing Network File System operations on Linux systems, including daemons that facilitate communication between clients and servers regarding file system states and identifiers. Within this suite, the fsidd daemon plays a critical role in handling requests related to filesystem identifier lookups via local domain sockets. This vulnerability stems from an improper input validation mechanism within the fsidd service logic. Specifically, the application relies on program assertions rather than robust error-handling routines to verify that required command arguments are present and correctly formatted before processing them. Assertions are typically intended for debugging purposes or catching internal programming errors under expected conditions, not as a primary defense against malformed external inputs. When an assertion fails, standard behavior in many production builds is to terminate the process immediately rather than returning a controlled error code to the caller.
A local user with access to the system can exploit this design flaw by crafting and sending a specifically malformed request over the local domain socket that lacks the mandatory arguments expected by the fsidd daemon. Because the service does not validate these inputs prior to reaching the assertion check, it proceeds directly to the failure point where the assertion triggers. This results in an immediate crash of the fsidd process. Since this daemon is responsible for handling filesystem identifier lookups, its termination disrupts any ongoing or pending operations that depend on this service. The impact is a localized Denial of Service condition affecting only those processes and users attempting to utilize the filesystem identification features provided by nfs-utils until the affected system administrator manually restarts the service.
From a classification perspective, this vulnerability aligns with CWE-617: Reachable Assertion, which describes situations where an assertion can be triggered by external input due to insufficient validation of preconditions. It also relates to CWE-20: Improper Input Validation, as the application fails to adequately sanitize or check user-supplied data before processing it in a security-critical manner. In terms of adversary tactics, this flaw supports techniques associated with ATT&CK T1499: Endpoint Denial of Service, specifically through resource exhaustion via service disruption rather than computational overload. An attacker could leverage this for simple denial-of-service attacks or potentially as part of a broader strategy to disrupt system stability and force administrative intervention during critical periods.
Mitigation strategies primarily involve ensuring that the nfs-utils package is updated to versions where developers have replaced assertion-based checks with proper input validation logic. Until such patches are applied, administrators should restrict access to the local domain socket used by fsidd to only trusted users or services, thereby limiting the attack surface available to potential exploiters. Additionally, implementing monitoring for unexpected daemon restarts can help detect exploitation attempts early, allowing for quicker response and recovery times in environments where immediate patching is not feasible.