CVE-2023-25826: OpenTSDB Remote Code Execution Vulnerability

CVE-2023-25826 Overview

CVE-2023-25826 is a command injection vulnerability in OpenTSDB that allows unauthenticated remote attackers to execute arbitrary operating system commands on vulnerable host systems. The vulnerability exists due to insufficient validation of parameters passed to the legacy HTTP query API, enabling attackers to inject crafted OS commands into multiple parameters and execute malicious code.

This exploit exists due to an incomplete fix that was made when this vulnerability was previously disclosed as CVE-2020-35476. The regex validation that was implemented to restrict allowed input to the query API does not work as intended, allowing crafted commands to bypass validation.

Critical Impact

Unauthenticated remote attackers can execute arbitrary commands on OpenTSDB host systems through the legacy HTTP query API, potentially leading to complete system compromise, data theft, or further network infiltration.

Affected Products

• OpenTSDB (all versions prior to the security fix)
• OpenTSDB version 2.4.1 and earlier

Discovery Timeline

• 2023-05-03 - CVE CVE-2023-25826 published to NVD
• 2025-02-13 - Last updated in NVD database

Technical Details for CVE-2023-25826

Vulnerability Analysis

This command injection vulnerability stems from inadequate input sanitization in OpenTSDB's legacy HTTP query API. The flaw is particularly concerning because it represents a regression—an incomplete fix for the previously disclosed CVE-2020-35476 vulnerability.

The attack requires no authentication and can be executed remotely over the network with minimal complexity. Successful exploitation grants attackers full control over confidentiality, integrity, and availability of the compromised system. The vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), which represents one of the most dangerous categories of security flaws.

Given the high EPSS score of 83.86% (99.28th percentile), this vulnerability has a significantly elevated probability of exploitation in the wild compared to most other CVEs, making immediate remediation essential.

Root Cause

The root cause is insufficient input validation in the legacy HTTP query API. When the original CVE-2020-35476 vulnerability was patched, regex-based validation was implemented to restrict allowed input. However, this regex validation is flawed and does not properly sanitize all malicious input patterns. Attackers can craft specially formatted commands that bypass the regex validation checks, allowing the injection of arbitrary OS commands that are then executed by the underlying system.

Attack Vector

The attack is network-based and can be executed by unauthenticated remote attackers. Malicious actors send specially crafted HTTP requests to the OpenTSDB legacy query API, embedding OS commands within parameters that are not properly validated. These commands bypass the incomplete regex filters and are passed to the underlying operating system shell for execution.

The exploitation flow involves:

1. An attacker identifies an exposed OpenTSDB instance with the legacy HTTP query API enabled
2. The attacker crafts HTTP requests with malicious OS command payloads embedded in API parameters
3. The inadequate regex validation fails to detect the malicious input
4. The injected commands are executed with the privileges of the OpenTSDB process
5. The attacker gains remote command execution on the host system

Detailed technical information about the exploitation technique is available in the Packet Storm exploit report and the Synopsys security blog post.

Detection Methods for CVE-2023-25826

Indicators of Compromise

• Unusual HTTP requests to the OpenTSDB legacy query API containing shell metacharacters or command sequences
• Unexpected child processes spawned by the OpenTSDB Java process
• Anomalous outbound network connections from OpenTSDB servers
• Evidence of command execution artifacts such as downloaded files, new user accounts, or modified system configurations

Detection Strategies

• Monitor HTTP request logs for the OpenTSDB query API, looking for suspicious characters like backticks, semicolons, pipe characters, and common command injection patterns
• Implement network intrusion detection rules to identify malicious payloads targeting the legacy HTTP query API
• Deploy application-level firewalls or web application firewalls (WAF) with rules to block command injection attempts
• Use endpoint detection and response (EDR) solutions to monitor for suspicious process execution chains originating from the OpenTSDB service

Monitoring Recommendations

• Enable detailed access logging for all OpenTSDB API endpoints and centralize logs for security analysis
• Configure alerting for any child process execution from the OpenTSDB Java runtime
• Monitor network traffic for unusual outbound connections from OpenTSDB host systems
• Implement file integrity monitoring on OpenTSDB servers to detect unauthorized changes

How to Mitigate CVE-2023-25826

Immediate Actions Required

• Apply the security patch from the official OpenTSDB repository immediately
• If immediate patching is not possible, disable or restrict access to the legacy HTTP query API
• Implement network-level access controls to limit which systems can reach the OpenTSDB query interface
• Review system logs for any evidence of prior exploitation attempts

Patch Information

The OpenTSDB development team has addressed this vulnerability in GitHub Pull Request #2275. Organizations running affected versions of OpenTSDB should review this pull request and apply the fix to their deployments. The patch implements improved input validation to properly sanitize parameters passed to the legacy HTTP query API, preventing the command injection attack vector.

Workarounds

• Disable the legacy HTTP query API if it is not required for your deployment
• Implement strict network segmentation to ensure OpenTSDB is only accessible from trusted internal networks
• Deploy a reverse proxy or web application firewall in front of OpenTSDB with rules to block requests containing shell metacharacters
• Run OpenTSDB with minimal system privileges to limit the impact of potential exploitation

# Network access restriction example using iptables
# Restrict access to OpenTSDB port (default 4242) to trusted IP ranges only
iptables -A INPUT -p tcp --dport 4242 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 4242 -j DROP