CVE-2026-76354 in Splunk
Summary
by MITRE • 08/20/2026
In Splunk Enterprise versions below 10.4.2, 10.2.6, 10.0.9, and 9.4.14, a user who does not hold the "admin" or "power" Splunk roles could affect system integrity and availability by sending a crafted Representational State Transfer (REST) API request that deletes or temporarily overwrites files writable by the user account running Splunk Enterprise processes on a non-captain search head cluster member. The vulnerability is possible because Search Head Clustering bundle replication does not validate the name of a replicated bundle file or neutralize NUL bytes before constructing the member bundle path. For more information see About search head clustering (https://help.splunk.com/en/splunk-enterprise/administer/distributed-search/10.4/overview-of-search-head-clustering/about-search-head-clustering), Define roles on the Splunk platform with capabilities (https://help.splunk.com/en/splunk-enterprise/administer/manage-users-and-security/10.4/manage-splunk-platform-users-and-roles/define-roles-on-the-splunk-platform-with-capabilities), and Secure Splunk Enterprise service accounts (https://help.splunk.com/en/splunk-enterprise/administer/manage-users-and-security/9.0/install-splunk-enterprise-securely/secure-splunk-enterprise-service-accounts) in the Splunk documentation.
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Analysis
by VulDB Data Team • 08/20/2026
A critical vulnerability exists within Splunk Enterprise versions prior to 10.4.2, 10.2.6, 10.0.9, and 9.4.14 that allows unprivileged users to compromise system integrity and availability through improper input validation in the Search Head Clustering mechanism. This flaw specifically affects non-captain search head cluster members where a user lacking admin or power roles can exploit insufficient path sanitization during bundle replication processes. The vulnerability stems from the failure of the application to validate file names received via Representational State Transfer API requests and its inability to neutralize NUL bytes before constructing the target member bundle path. This lack of rigorous input validation creates an opportunity for attackers to manipulate filesystem operations in ways that were not intended by the software architecture, leading to potential data loss or service disruption within the distributed search environment.
The technical root cause lies in how Splunk handles file paths during the replication of configuration bundles across cluster members. When a REST API request is processed to update bundle files, the system constructs local filesystem paths based on input parameters without adequately checking for directory traversal sequences or null byte injection techniques. By sending crafted requests containing maliciously formatted filenames that include NUL bytes or path separators such as dots and slashes, an attacker can redirect file write operations outside of the designated secure directories. This allows the user account running Splunk Enterprise processes to inadvertently delete critical configuration files or temporarily overwrite them with arbitrary content. Since this operation occurs on a non-captain search head cluster member, it disrupts the synchronization process essential for maintaining consistent configurations across the entire cluster, thereby undermining the reliability of the distributed search infrastructure.
From an operational perspective, the impact of this vulnerability is significant as it directly affects both data integrity and service availability. An attacker who successfully exploits this flaw can cause a denial of service by deleting or corrupting configuration files required for normal Splunk operations on affected nodes. This may result in individual cluster members becoming unresponsive or failing to participate correctly in search head clustering, which degrades the overall performance and resilience of the logging and security analytics platform. Furthermore, if critical system files are overwritten with malicious content, it could potentially lead to further exploitation vectors depending on how those files are subsequently processed by other components within the Splunk ecosystem. The ability for low-privilege users to perform such destructive actions highlights a severe gap in role-based access control enforcement and input validation protocols within the affected versions of the software.
To mitigate this risk, organizations running vulnerable versions of Splunk Enterprise must immediately upgrade to version 10.4.2 or later, where these path validation issues have been addressed by the vendor. In addition to applying patches, administrators should review their role definitions and capabilities to ensure that users without administrative privileges do not possess unnecessary access to REST API endpoints involved in bundle replication operations. It is also recommended to adhere to best practices for securing Splunk Enterprise service accounts as outlined in official documentation, including restricting file system permissions so that the user account running Splunk processes has minimal write access limited strictly to necessary directories. Regular auditing of API usage and monitoring for anomalous file modification patterns can provide additional layers of defense against exploitation attempts targeting this class of vulnerabilities.
This vulnerability aligns with Common Weakness Enumeration categories such as CWE-20 Improper Input Validation, which describes the failure to verify that input data meets expected format constraints before processing. Additionally, it relates to CWE-73 External Control of File Name or Path, reflecting the ability for an attacker to influence file system operations through manipulated path components. In terms of attack tactics, this exploitation method corresponds to ATT&CK technique T1564.002 Hidden Files and Directories, as attackers may use NUL bytes to obscure malicious files from standard directory listings, and potentially T1489 Service Stop if the goal is to disrupt availability by deleting essential configuration files. Understanding these mappings helps security teams contextualize the threat within broader cybersecurity frameworks and prioritize remediation efforts accordingly based on industry-standard classification systems.