Splunk Enterprise and Cloud Platform Information Disclosure Vulnerability (CVE-2026-20239)

Splunk Enterprise and Splunk Cloud Platform are affected by an information disclosure vulnerability, identified as CVE-2026-20239. The vulnerability resides in Splunk Enterprise versions prior to 10.2.2 and 10.0.5, as well as Splunk Cloud Platform versions below 10.3.2512.8, 10.2.2510.11, 10.1.2507.21, and 10.0.2503.13. A user with a role that has access to the _internal index can exploit this vulnerability to view session cookies and response bodies, potentially exposing sensitive data. This can lead to unauthorized access or compromise of user accounts and sensitive information. Defenders should ensure Splunk instances are updated to the latest versions to mitigate this vulnerability.

Attack Chain

1. An attacker gains unauthorized access to a Splunk instance.
2. The attacker obtains a role with permissions to access the _internal index.
3. The attacker queries the _internal index, specifically targeting logs containing session cookies or response bodies.
4. The vulnerable Splunk versions do not properly sanitize or restrict access to sensitive data within these logs.
5. Session cookies, which may contain authentication tokens, are exposed to the attacker.
6. Response bodies, potentially including API responses or other sensitive communications, are revealed.
7. The attacker extracts the sensitive data, such as session tokens or API keys, from the exposed logs.

Impact

Successful exploitation of CVE-2026-20239 allows a user with access to the _internal index to view sensitive information like session cookies and response bodies within Splunk logs. This could lead to account compromise, unauthorized access to systems and data, and further escalation of privileges. The impact is significant as it directly affects the confidentiality of data processed and stored within Splunk environments. Organizations using vulnerable Splunk versions are at risk of data breaches and compliance violations.

Recommendation

• Upgrade Splunk Enterprise instances to version 10.2.2 or later, or 10.0.5 or later to remediate CVE-2026-20239.
• Upgrade Splunk Cloud Platform instances to version 10.3.2512.8, 10.2.2510.11, 10.1.2507.21, or 10.0.2503.13 to remediate CVE-2026-20239.
• Review and restrict access to the _internal index to only authorized personnel with a legitimate need to access this data.
• Deploy the Sigma rule “Detect Splunk Internal Index Access” to monitor for suspicious access patterns to the _internal index.