CVE-2021-27258: SolarWinds Orion Privilege Escalation Flaw

CVE-2021-27258 Overview

CVE-2021-27258 is a critical privilege escalation vulnerability affecting SolarWinds Orion Platform 2020.2. This vulnerability allows remote attackers to escalate privileges on affected installations without requiring any authentication. The specific flaw exists within the SaveUserSetting endpoint, which lacks proper restrictions to prevent unprivileged users from accessing privileged functionality. An attacker can leverage this vulnerability to escalate their privileges from Guest to Administrator, potentially gaining full control over the Orion Platform environment.

Critical Impact

Unauthenticated remote attackers can escalate privileges from Guest to Administrator on SolarWinds Orion Platform 2020.2 by exploiting the improperly restricted SaveUserSetting endpoint.

Affected Products

• SolarWinds Orion Platform 2020.2

Discovery Timeline

• 2021-04-14 - CVE CVE-2021-27258 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-27258

Vulnerability Analysis

This vulnerability represents a Broken Access Control flaw (CWE-284: Improper Access Control) in the SolarWinds Orion Platform. The SaveUserSetting endpoint fails to implement proper authorization checks, allowing unprivileged users to modify user settings that should be restricted to administrative users only.

The vulnerability is particularly severe because it requires no authentication to exploit. An attacker with network access to the Orion Platform can directly interact with the SaveUserSetting endpoint and manipulate user privilege levels. This design flaw enables complete privilege escalation from the lowest privilege level (Guest) to the highest (Administrator).

Given SolarWinds Orion Platform's role as a critical IT infrastructure monitoring solution deployed across enterprise environments, successful exploitation could provide attackers with extensive access to network monitoring data, configuration settings, and the ability to modify alerting and monitoring policies.

Root Cause

The root cause of CVE-2021-27258 is the improper restriction of the SaveUserSetting endpoint to unprivileged users. The endpoint lacks proper authorization validation, failing to verify that the requesting user has sufficient privileges before processing user setting modifications. This missing access control check allows any user, including unauthenticated guests, to modify settings that should only be accessible to administrators.

Attack Vector

The attack leverages the network-accessible SaveUserSetting endpoint to perform unauthorized privilege modifications. An attacker can send crafted requests to this endpoint without authentication, manipulating user role assignments or privilege settings to escalate their access level.

The attack flow involves:

1. Identifying a vulnerable SolarWinds Orion Platform 2020.2 installation accessible over the network
2. Sending malicious requests to the SaveUserSetting endpoint without authentication
3. Modifying user privilege settings to elevate a Guest account to Administrator status
4. Gaining full administrative access to the Orion Platform

For detailed technical information about this vulnerability, refer to the Zero Day Initiative Advisory ZDI-21-192.

Detection Methods for CVE-2021-27258

Indicators of Compromise

• Unexpected privilege changes for user accounts, particularly Guest accounts being elevated to Administrator
• Unusual or unauthorized requests to the SaveUserSetting endpoint in web server logs
• New administrator accounts or modified user settings without corresponding change requests
• Anomalous network traffic patterns targeting the Orion Platform management interface

Detection Strategies

• Monitor web application logs for requests to the SaveUserSetting endpoint, especially from unauthenticated sessions or Guest users
• Implement alerting for any privilege escalation events or user role modifications in the Orion Platform
• Deploy network-based intrusion detection rules to identify exploit attempts targeting this endpoint
• Audit user account privileges regularly to detect unauthorized elevations

Monitoring Recommendations

• Enable verbose logging on the SolarWinds Orion Platform web services to capture all endpoint requests
• Implement SIEM rules to correlate authentication events with privilege modification attempts
• Configure alerts for any administrative actions performed by accounts that were recently Guest-level users
• Monitor for bulk or automated requests to user management endpoints

How to Mitigate CVE-2021-27258

Immediate Actions Required

• Identify all SolarWinds Orion Platform 2020.2 installations in your environment
• Restrict network access to the Orion Platform management interface to trusted IP addresses only
• Review user accounts for unauthorized privilege escalations and revoke any suspicious administrative access
• Apply available security patches from SolarWinds immediately

Patch Information

SolarWinds has addressed this vulnerability in subsequent releases of the Orion Platform. Organizations should update to the latest patched version of SolarWinds Orion Platform as soon as possible. Refer to the Zero Day Initiative Advisory ZDI-21-192 for additional details on the vulnerability and remediation guidance.

Workarounds

• Implement network segmentation to restrict access to the Orion Platform management interface from untrusted networks
• Deploy a web application firewall (WAF) with rules to block unauthorized requests to the SaveUserSetting endpoint
• Disable Guest access to the Orion Platform if not required for business operations
• Enable multi-factor authentication for all Orion Platform administrative accounts

# Example: Restrict access to Orion Platform management interface via firewall
# Adjust IP ranges according to your trusted administrative network
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP