CVE-2026-20142: Splunk Enterprise Information Disclosure

CVE-2026-20142 Overview

A sensitive information disclosure vulnerability exists in Splunk Enterprise that allows users with access to the Splunk _internal index within a Search Head Cluster (SHC) deployment to view RSA accessKey values from the Authentication.conf file in plain text. This vulnerability (CWE-532: Insertion of Sensitive Information into Log File) enables privileged users to potentially access cryptographic key material that should remain protected.

Critical Impact

Exposure of RSA access keys could allow attackers to compromise authentication mechanisms, potentially leading to unauthorized access to sensitive systems and data within the Splunk infrastructure.

Affected Products

• Splunk Enterprise versions below 10.2.0
• Splunk Enterprise versions below 10.0.2, 9.4.7, 9.3.9, and 9.2.11
• Splunk Search Head Cluster (SHC) deployments

Discovery Timeline

• 2026-02-18 - CVE CVE-2026-20142 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-20142

Vulnerability Analysis

This vulnerability stems from improper handling of sensitive authentication credentials within Splunk Enterprise's Search Head Cluster deployments. The RSA accessKey value stored in the Authentication.conf configuration file is logged or stored in a manner that makes it accessible through the _internal index. Users with legitimate access to this index for monitoring purposes can inadvertently or intentionally view these cryptographic keys in plain text.

The attack requires adjacent network access and high privileges, as the attacker must already have a role with access to the _internal index. However, once this access is obtained, the exposure of RSA keys could have cascading security implications including the ability to forge authentication tokens or bypass security controls.

Root Cause

The root cause is the insertion of sensitive information (RSA access keys) into log files or internal indices without proper redaction or encryption. This violates the principle of least privilege by exposing cryptographic material to users who may have legitimate operational reasons to access internal logs but should not have visibility into authentication secrets. The Authentication.conf file contains sensitive security configuration data that should never be exposed in searchable indices.

Attack Vector

The vulnerability is exploitable from an adjacent network position by an authenticated user with high privileges. An attacker who has obtained access to a role with _internal index permissions can craft search queries to extract the RSA accessKey values from logged configuration data. This does not require user interaction and operates within the scope of the attacker's existing access level, though the confidentiality, integrity, and availability impact is considered high due to the sensitive nature of the exposed credentials.

The attack scenario involves:

1. An attacker gaining access to a Splunk user account with _internal index read permissions
2. Executing search queries against the _internal index to locate configuration data
3. Extracting plain text RSA access keys from the Authentication.conf file entries
4. Using the exposed keys to potentially compromise authentication mechanisms

Detection Methods for CVE-2026-20142

Indicators of Compromise

• Unusual search queries against the _internal index targeting Authentication.conf or authentication-related fields
• Access to _internal index by users who don't typically require this access for their role
• Queries specifically searching for terms like accessKey, RSA, or authentication configuration parameters
• Bulk data exports or saves from _internal index search results

Detection Strategies

• Implement audit logging for all searches performed against the _internal index
• Create alerts for searches containing keywords related to authentication configuration (e.g., accessKey, Authentication.conf, RSA)
• Monitor user access patterns to the _internal index and flag anomalous behavior
• Review role assignments periodically to ensure only necessary personnel have _internal index access

Monitoring Recommendations

• Enable comprehensive search logging within Splunk to capture all queries against sensitive indices
• Deploy real-time alerts for potential credential harvesting search patterns
• Implement user behavior analytics to detect privilege abuse scenarios
• Regularly audit and review access control lists for the _internal index

How to Mitigate CVE-2026-20142

Immediate Actions Required

• Upgrade Splunk Enterprise to version 10.2.0 or later immediately
• For version 10.0.x, upgrade to 10.0.2 or later
• For version 9.4.x, upgrade to 9.4.7 or later
• For version 9.3.x, upgrade to 9.3.9 or later
• For version 9.2.x, upgrade to 9.2.11 or later
• Review and restrict role assignments that grant access to the _internal index
• Rotate any RSA access keys that may have been exposed

Patch Information

Splunk has released security updates addressing this vulnerability. Detailed patch information and upgrade instructions are available in the Splunk Security Advisory SVD-2026-0207. Administrators should follow standard Splunk upgrade procedures while ensuring proper backup and rollback plans are in place.

Workarounds

• Restrict access to the _internal index by modifying role capabilities to limit who can search this index
• Implement stricter access controls on roles that require any level of internal monitoring access
• Consider network segmentation to limit adjacent network access to SHC deployments
• Enable additional logging and monitoring for any access to sensitive indices until patches can be applied
• Review and rotate authentication credentials as a precautionary measure

# Example: Restrict _internal index access in authorize.conf
# Location: $SPLUNK_HOME/etc/system/local/authorize.conf

[role_restricted_user]
# Remove _internal from allowed indexes
srchIndexesAllowed = main;summary
# Explicitly deny _internal access
srchIndexesDisallowed = _internal;_audit