CVE-2026-76348 Overview
CVE-2026-76348 is a missing authorization vulnerability [CWE-862] in Splunk Enterprise. The flaw affects Search Head Cluster (SHC) member control endpoints, which apply read-only authorization without validating the Hypertext Transfer Protocol (HTTP) request type. An authenticated user holding a Splunk role with the list_search_head_clustering capability can send a read request that changes cluster state. The resulting state modification can trigger a denial of service on the Search Head Cluster.
The issue impacts Splunk Enterprise versions below 10.4.2, 10.2.6, 10.0.9, and 9.4.14. Splunk documented the flaw in advisory SVD-2026-0801.
Critical Impact
An authenticated high-privilege user can alter Search Head Cluster state through read-only endpoints, causing a denial of service.
Affected Products
- Splunk Enterprise versions below 10.4.2 (10.4.x branch)
- Splunk Enterprise versions below 10.2.6 and 10.0.9 (10.x branches)
- Splunk Enterprise versions below 9.4.14 (9.4.x branch)
Discovery Timeline
- 2026-08-19 - CVE-2026-76348 published to NVD
- 2026-08-20 - Last updated in NVD database
Technical Details for CVE-2026-76348
Vulnerability Analysis
Splunk Search Head Cluster (SHC) coordinates multiple search heads for high availability and load distribution. Member control endpoints expose administrative functions that can promote, demote, or reconfigure cluster members. These endpoints should require state-changing HTTP methods such as POST or PUT before applying authorization for privileged actions.
The endpoints instead apply read-only authorization to requests that ultimately mutate cluster state. A user with the list_search_head_clustering capability, which is documented as a listing-only permission, can invoke functions that reconfigure cluster members. The mismatch between the intent of the capability and the effect of the endpoint enables denial of service against the cluster.
The attack requires an authenticated account and a Splunk role that includes the high-privilege capability. Exploitation is limited to availability impact; the vulnerability does not expose confidential data or permit arbitrary integrity changes beyond cluster state.
Root Cause
The root cause is missing authorization enforcement tied to HTTP method [CWE-862]. Splunk applies read authorization to endpoints that can trigger writes. The list_search_head_clustering capability grants access broader than its name implies because the endpoints do not distinguish safe read methods (GET, HEAD) from unsafe state-changing methods.
Attack Vector
An attacker authenticates to a Splunk Enterprise instance using an account that has been granted the list_search_head_clustering capability. The attacker issues a read request to a Search Head Cluster member control endpoint. The endpoint processes the request and modifies cluster state, disrupting search availability across the cluster. Refer to the Splunk Security Advisory SVD-2026-0801 for endpoint specifics.
Detection Methods for CVE-2026-76348
Indicators of Compromise
- Unexpected Search Head Cluster state transitions, member reassignments, or captain elections recorded in splunkd.log outside of planned maintenance windows.
- Access log entries in access.log showing requests to Search Head Cluster member control endpoints from accounts assigned the list_search_head_clustering capability.
- Search head unavailability, failed distributed searches, or replication errors coinciding with authenticated API activity.
Detection Strategies
- Audit Splunk role assignments and identify every account that holds the list_search_head_clustering capability. Alert on additions to those roles.
- Correlate _audit index entries with SHC state-change events in _internal to surface requests that changed cluster state via read methods.
- Baseline normal SHC administrative activity and alert on off-hours or non-administrator invocations of cluster control endpoints.
Monitoring Recommendations
- Forward Splunk _audit and _internal indexes to a centralized SIEM for retention and cross-correlation.
- Monitor Search Head Cluster health status metrics and generate alerts on unplanned captain changes or rolling restarts.
- Track authentication events for accounts with clustering capabilities and enforce alerting on privilege escalation attempts.
How to Mitigate CVE-2026-76348
Immediate Actions Required
- Upgrade Splunk Enterprise to version 10.4.2, 10.2.6, 10.0.9, 9.4.14, or later according to the deployed release branch.
- Review all custom Splunk roles and revoke the list_search_head_clustering capability from accounts that do not require cluster administration.
- Enforce multi-factor authentication on Splunk accounts that retain clustering capabilities.
Patch Information
Splunk released fixed builds in advisory SVD-2026-0801. The fixed versions are Splunk Enterprise 10.4.2, 10.2.6, 10.0.9, and 9.4.14. Consult the Splunk Security Advisory SVD-2026-0801 for the complete patch matrix and upgrade guidance.
Workarounds
- Restrict the list_search_head_clustering capability to trusted administrative roles only until patching is complete.
- Place Splunk management interfaces behind network segmentation and permit access only from administrative jump hosts.
- Rotate credentials for any privileged Splunk account that may have been shared or exposed prior to patching.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
