CVE-2023-4310: BeyondTrust Privileged Remote Access RCE

CVE-2023-4310 Overview

CVE-2023-4310 is a critical command injection vulnerability affecting BeyondTrust Privileged Remote Access (PRA) and Remote Support (RS) versions 23.2.1 and 23.2.2. The vulnerability can be exploited through a malicious HTTP request, allowing an unauthenticated remote attacker to execute underlying operating system commands within the context of the site user. This vulnerability poses a significant risk to organizations utilizing these remote access solutions for privileged session management and technical support operations.

Critical Impact

Unauthenticated remote attackers can execute arbitrary operating system commands on affected BeyondTrust appliances, potentially leading to complete system compromise, data exfiltration, and lateral movement within enterprise networks.

Affected Products

• BeyondTrust Privileged Remote Access version 23.2.1
• BeyondTrust Privileged Remote Access version 23.2.2
• BeyondTrust Remote Support version 23.2.1
• BeyondTrust Remote Support version 23.2.2

Discovery Timeline

• September 5, 2023 - CVE-2023-4310 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-4310

Vulnerability Analysis

This vulnerability falls under CWE-77 (Improper Neutralization of Special Elements used in a Command), commonly known as command injection. The flaw exists in how the BeyondTrust PRA and RS applications process HTTP requests, failing to properly sanitize user-supplied input before passing it to operating system command interpreters.

The vulnerability is particularly severe because it requires no authentication, meaning any remote attacker with network access to the vulnerable appliance can exploit it. Successful exploitation allows command execution within the context of the site user, which typically has elevated privileges necessary for the remote access functionality to operate correctly.

Root Cause

The root cause stems from insufficient input validation and sanitization in the HTTP request handling components of BeyondTrust PRA and RS. When processing certain HTTP requests, the application fails to properly neutralize special characters and command sequences that are subsequently interpreted by the underlying operating system shell. This allows attackers to inject arbitrary commands that are executed with the privileges of the application's service account.

Attack Vector

The attack is network-based and can be initiated remotely without any authentication or user interaction. An attacker can craft a malicious HTTP request containing operating system commands embedded within request parameters or headers. When the vulnerable application processes this request, the injected commands are passed to the operating system shell for execution.

The attack flow typically involves:

1. Identifying an exposed BeyondTrust PRA or RS instance running a vulnerable version
2. Crafting an HTTP request with embedded OS commands in vulnerable parameters
3. Sending the malicious request to the target appliance
4. The application processes the request without proper sanitization
5. Injected commands execute with site user privileges on the underlying system

Since no public exploit code is currently available, specific technical details regarding the vulnerable parameters have not been disclosed. For detailed technical information, refer to the BeyondTrust Knowledge Base Article and the BeyondTrust Security Update Blog.

Detection Methods for CVE-2023-4310

Indicators of Compromise

• Unusual outbound network connections from BeyondTrust appliances to unexpected destinations
• Anomalous process spawning from the BeyondTrust application service account
• Unexpected modifications to system files or configuration on BeyondTrust servers
• Web access logs showing malformed or unusually long HTTP requests with shell metacharacters

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block HTTP requests containing common command injection patterns such as shell metacharacters (;, |, &, $(), backticks)
• Monitor BeyondTrust server process trees for unexpected child processes spawned by the application
• Enable and review comprehensive HTTP access logging for anomalous request patterns
• Deploy network intrusion detection signatures to identify command injection attempt patterns

Monitoring Recommendations

• Establish baseline behavior for BeyondTrust appliances and alert on deviations in process execution, network connections, or file system activity
• Configure SIEM rules to correlate HTTP request anomalies with subsequent suspicious process or network activity on BeyondTrust hosts
• Monitor for authentication events, privilege escalation attempts, and lateral movement originating from BeyondTrust infrastructure

How to Mitigate CVE-2023-4310

Immediate Actions Required

• Immediately identify all BeyondTrust Privileged Remote Access and Remote Support installations running versions 23.2.1 or 23.2.2
• Upgrade affected systems to version 23.2.3 or later as soon as possible
• Implement network segmentation to restrict access to BeyondTrust management interfaces to authorized IP ranges only
• Review logs for indicators of compromise to determine if exploitation has already occurred

Patch Information

BeyondTrust has addressed this vulnerability in version 23.2.3. Organizations should upgrade all affected Privileged Remote Access and Remote Support installations to this version or later immediately. Detailed upgrade instructions and release notes are available through the BeyondTrust Knowledge Base and the official BeyondTrust Security Blog.

Workarounds

• Restrict network access to BeyondTrust appliances using firewall rules to allow connections only from trusted IP addresses and networks
• Place BeyondTrust appliances behind a reverse proxy or WAF configured to inspect and filter malicious HTTP requests
• Enable enhanced logging and monitoring on BeyondTrust systems until patching can be completed
• Consider temporarily disabling internet-facing access to vulnerable appliances if immediate patching is not feasible

# Example firewall rule to restrict access to BeyondTrust appliance
# Replace IP ranges with your organization's trusted networks
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.0.0/16 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP