CVE-2026-76251: Splunk Enterprise Auth Bypass Vulnerability

CVE-2026-76251 Overview

CVE-2026-76251 is a missing authorization vulnerability [CWE-862] in Splunk Enterprise that affects the Splunk App for Splunk Observability Cloud. A low-privileged user without the admin or power role can force the app to forward requests to Splunk Observability Cloud using the stored access token. The forwarded requests inherit the token's permissions, allowing the attacker to view data and make limited changes to Observability Cloud content. The vulnerability stems from Representational State Transfer (REST) API endpoint handlers that fail to enforce the read_o11y_content capability before proxying requests.

Critical Impact
Authenticated low-privilege users can access Splunk Observability Cloud data and modify content by abusing the stored access token in the Observability Cloud app.

Affected Products

Splunk Enterprise versions below 10.4.2
Splunk Enterprise versions below 10.2.6
Splunk Enterprise versions below 10.0.9

Discovery Timeline

2026-08-19 - CVE-2026-76251 published to NVD
2026-08-20 - Last updated in NVD database

Technical Details for CVE-2026-76251

Vulnerability Analysis

The Splunk App for Splunk Observability Cloud exposes REST API endpoints that proxy requests from Splunk Enterprise to Splunk Observability Cloud. These endpoints attach a stored access token before forwarding the request. The handlers do not check whether the caller holds the read_o11y_content capability, so any authenticated user can invoke them.

Because the app appends its own access token, the destination service authorizes the request based on the token's scope rather than the calling user's role. This allows a user without admin or power privileges to read data and modify limited content in Splunk Observability Cloud. Splunk Enterprise 9.4 and 9.3 releases are not affected.

Root Cause

The root cause is a missing authorization check in the app's REST endpoint handlers. The code path that forwards requests to Splunk Observability Cloud does not gate execution on the read_o11y_content capability. This is a classic [CWE-862] Missing Authorization defect where role-based capability enforcement was omitted before a privileged action.

Attack Vector

An attacker requires network access to Splunk Enterprise and valid credentials for any role. The attacker sends a crafted request to a vulnerable REST endpoint exposed by the Splunk App for Splunk Observability Cloud. The app forwards the request with the embedded access token, returning Observability Cloud data or applying limited modifications. No user interaction is required beyond the initial authenticated session.

No public exploit code or proof-of-concept has been published. See the Splunk Security Advisory SVD-2026-0801 for vendor-supplied technical details.

Detection Methods for CVE-2026-76251

Indicators of Compromise

Unexpected REST API calls to Splunk App for Splunk Observability Cloud endpoints from non-admin, non-power role accounts.
Outbound requests from Splunk Enterprise to Splunk Observability Cloud endpoints correlated with low-privilege user sessions.
Modifications to Splunk Observability Cloud content lacking a corresponding administrative action in Splunk Enterprise audit logs.

Detection Strategies

Review audit.log and splunkd_access.log for REST calls to Observability Cloud app endpoints and correlate the invoking user's assigned roles.
Alert when accounts without the read_o11y_content capability trigger requests that result in outbound traffic to Splunk Observability Cloud.
Baseline normal usage of the Observability Cloud app and flag deviations tied to non-privileged users.

Monitoring Recommendations

Enable verbose REST endpoint logging for the Splunk App for Splunk Observability Cloud and forward logs to a central SIEM.
Monitor Splunk Observability Cloud audit trails for API activity attributable to the shared app token and reconcile against expected administrator actions.
Track any content changes in Splunk Observability Cloud and require an approved change request for correlation.

How to Mitigate CVE-2026-76251

Immediate Actions Required

Upgrade Splunk Enterprise to 10.4.2, 10.2.6, or 10.0.9 or later, depending on the deployed branch.
Audit user role assignments and remove the Splunk App for Splunk Observability Cloud access from users who do not require it.
Rotate the Splunk Observability Cloud access token stored in the app after patching to invalidate any previously exposed credentials.

Patch Information

Splunk has released fixed versions 10.4.2, 10.2.6, and 10.0.9 that enforce the read_o11y_content capability in the affected REST endpoint handlers. Refer to the Splunk Security Advisory SVD-2026-0801 for official patch guidance and download links.

Workarounds

Restrict access to the Splunk App for Splunk Observability Cloud to users with the admin or power role until patches can be applied.
Disable the Splunk App for Splunk Observability Cloud on affected Splunk Enterprise instances if the integration is not actively used.
Apply role-based capability restrictions to limit which users can invoke Observability Cloud REST endpoints, per the Splunk capabilities documentation.

bash

# Example: list users and roles to identify accounts with unnecessary app access
/opt/splunk/bin/splunk list user -auth admin:<password>

# Example: remove a role from a user until patching is complete
/opt/splunk/bin/splunk edit user <username> -role <restricted-role> -auth admin:<password>