CVE-2024-29945: Splunk Enterprise Token Disclosure Flaw

CVE-2024-29945 Overview

CVE-2024-29945 is a sensitive information disclosure vulnerability affecting Splunk Enterprise. The software potentially exposes authentication tokens during the token validation process when either Splunk Enterprise runs in debug mode or the JsonWebToken component has been configured to log its activity at the DEBUG logging level. This vulnerability allows attackers with access to log files to capture authentication tokens, potentially leading to unauthorized access and privilege escalation within Splunk deployments.

Critical Impact

Authentication tokens logged in debug mode can be harvested by attackers to gain unauthorized access to Splunk Enterprise environments, potentially compromising sensitive data and administrative functions.

Affected Products

• Splunk Enterprise versions below 9.2.1
• Splunk Enterprise versions below 9.1.4
• Splunk Enterprise versions below 9.0.9

Discovery Timeline

• 2024-03-27 - CVE-2024-29945 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-29945

Vulnerability Analysis

This vulnerability is classified under CWE-532 (Insertion of Sensitive Information into Log File), representing a significant information leakage issue in Splunk Enterprise's token handling mechanism. The flaw occurs within the authentication token validation workflow, where sensitive JWT (JSON Web Token) credentials are inadvertently written to log files under specific debugging configurations.

The vulnerability requires network access and elevated privileges to exploit effectively, though the potential impact includes compromise of confidentiality, integrity, and availability of the Splunk system. When debug logging is enabled—either through running Splunk Enterprise in debug mode or configuring the JsonWebToken component with DEBUG-level logging—authentication tokens are captured in plaintext within log files. These tokens can then be extracted by malicious actors who gain access to the log files.

Root Cause

The root cause stems from improper handling of sensitive authentication data in the logging subsystem. The JsonWebToken component, when operating at DEBUG logging levels, fails to sanitize or redact authentication tokens before writing diagnostic information to logs. This design oversight means that authentication credentials intended to be ephemeral and protected are persisted in readable format within log storage.

The vulnerability is particularly concerning in enterprise environments where log files may be aggregated, backed up, or accessible to multiple administrators, expanding the potential attack surface for token theft.

Attack Vector

The attack requires network access and typically privileged access to the Splunk environment. An attacker would first need to either enable debug mode on the target Splunk Enterprise instance or have access to an environment where debug logging is already enabled. Once debug logging is active, the attacker monitors or retrieves log files containing the exposed authentication tokens.

The attacker can then extract valid JWT tokens from the logs and replay them to authenticate as legitimate users without knowing their credentials. This enables session hijacking, privilege escalation, and unauthorized access to sensitive data indexed within Splunk. The attack is most effective when combined with other vulnerabilities or misconfigurations that allow access to Splunk log files.

Detection Methods for CVE-2024-29945

Indicators of Compromise

• Unexpected DEBUG-level logging enabled on Splunk Enterprise instances or JsonWebToken components
• Suspicious access patterns to Splunk internal log files ($SPLUNK_HOME/var/log/splunk/)
• Authentication events from unexpected IP addresses or at unusual times using valid tokens
• Evidence of log file exfiltration or unauthorized access to log storage locations

Detection Strategies

• Monitor for changes to logging configuration that enable DEBUG mode on authentication-related components
• Implement file integrity monitoring on Splunk log directories to detect unauthorized access
• Review authentication logs for token reuse patterns that may indicate token theft and replay attacks
• Use Splunk's own detection capabilities as documented in the Splunk Research Application Analysis

Monitoring Recommendations

• Establish baseline logging levels and alert on any configuration changes to DEBUG mode
• Implement access controls and auditing for Splunk log file directories
• Deploy SentinelOne to monitor endpoint activity for suspicious access to sensitive log files
• Configure SIEM alerts for unusual authentication patterns that may indicate token replay attacks

How to Mitigate CVE-2024-29945

Immediate Actions Required

• Upgrade Splunk Enterprise to version 9.2.1, 9.1.4, or 9.0.9 or later immediately
• Review current logging configurations and disable DEBUG-level logging on JsonWebToken components and Splunk Enterprise
• Rotate all authentication tokens that may have been exposed during periods when debug logging was enabled
• Restrict access to Splunk log file directories to authorized personnel only

Patch Information

Splunk has released security patches addressing this vulnerability. Organizations should upgrade to the following versions:

• Splunk Enterprise 9.2.1 or later (for 9.2.x branch)
• Splunk Enterprise 9.1.4 or later (for 9.1.x branch)
• Splunk Enterprise 9.0.9 or later (for 9.0.x branch)

Refer to the official Splunk Security Advisory SVD-2024-0301 for complete patching instructions and release notes.

Workarounds

• Ensure Splunk Enterprise is not running in debug mode in production environments
• Set JsonWebToken component logging to INFO or WARN level to prevent token exposure
• Implement strict file permissions on log directories to limit access to essential personnel
• Consider implementing log rotation with secure deletion to minimize the window of exposure for any logged tokens

# Configuration example
# Verify and set appropriate logging levels in server.conf
# Navigate to $SPLUNK_HOME/etc/system/local/
# Check server.conf for logging settings

# Ensure debug mode is disabled
cat $SPLUNK_HOME/etc/system/local/server.conf | grep -i debug

# Verify log directory permissions
ls -la $SPLUNK_HOME/var/log/splunk/
chmod 700 $SPLUNK_HOME/var/log/splunk/

# Restart Splunk after configuration changes
$SPLUNK_HOME/bin/splunk restart