CVE-2020-27130: Cisco Security Manager Path Traversal Flaw

CVE-2020-27130 Overview

A critical path traversal vulnerability exists in Cisco Security Manager that could allow an unauthenticated, remote attacker to gain access to sensitive information. The vulnerability is due to improper validation of directory traversal character sequences within requests to an affected device. An attacker could exploit this vulnerability by sending a crafted request to the affected device. A successful exploit could allow the attacker to download arbitrary files from the affected device.

Critical Impact

Unauthenticated remote attackers can download arbitrary files from vulnerable Cisco Security Manager installations, potentially exposing sensitive configuration data, credentials, and other critical infrastructure information.

Affected Products

• Cisco Security Manager (all vulnerable versions)

Discovery Timeline

• 2020-11-17 - CVE-2020-27130 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-27130

Vulnerability Analysis

This vulnerability falls into the category of Directory Traversal (CWE-35), a classic web application security flaw that occurs when user-supplied input is not properly sanitized before being used to construct file paths. In the case of Cisco Security Manager, the application fails to adequately validate directory traversal character sequences (such as ../ or ..\) within incoming HTTP requests.

The vulnerability allows attackers to break out of the intended directory structure and access files located elsewhere on the file system. This can lead to significant information disclosure, including sensitive configuration files, credentials, database contents, and potentially other critical system information that could be leveraged for further attacks.

Root Cause

The root cause of this vulnerability is improper input validation within Cisco Security Manager's request handling mechanism. The application does not adequately sanitize or validate user-supplied input for directory traversal sequences before using that input to construct file paths. This allows malicious actors to inject path manipulation characters that navigate outside the intended web root or application directory.

Specifically, the application fails to:

• Properly sanitize or reject path traversal sequences such as ../, ..\, or URL-encoded variants
• Implement proper path canonicalization before file access operations
• Restrict file access to only authorized directories

Attack Vector

The attack can be executed remotely over the network without any authentication requirements. An attacker would craft malicious HTTP requests containing directory traversal sequences targeting the vulnerable Cisco Security Manager instance. The crafted requests would manipulate file path parameters to traverse directories and access files outside the intended scope.

For example, an attacker might manipulate URL parameters or request paths to include sequences like ../../../etc/passwd or similar patterns to access sensitive system files. The attack requires no user interaction and can be performed by any network-accessible attacker who can reach the vulnerable Cisco Security Manager web interface.

The exploitation technique typically involves:

1. Identifying a vulnerable Cisco Security Manager instance
2. Crafting HTTP requests with directory traversal payloads
3. Sending requests to the target system
4. Retrieving sensitive files from the response

For detailed technical information, refer to the Cisco Security Advisory.

Detection Methods for CVE-2020-27130

Indicators of Compromise

• HTTP requests containing directory traversal sequences such as ../, ..\, %2e%2e%2f, or %2e%2e/ in URL parameters or paths targeting Cisco Security Manager
• Unusual access patterns to the Cisco Security Manager web interface from untrusted IP addresses
• Log entries showing requests attempting to access files outside the web application root directory
• Successful retrieval of system configuration files or sensitive data from unexpected sources

Detection Strategies

• Deploy web application firewall (WAF) rules to detect and block requests containing path traversal patterns
• Enable detailed logging on Cisco Security Manager and monitor for suspicious request patterns
• Implement network intrusion detection signatures for common directory traversal attack payloads
• Review access logs for requests containing encoded or double-encoded traversal sequences

Monitoring Recommendations

• Configure SIEM alerts for HTTP requests containing ../ or encoded equivalents targeting Cisco Security Manager endpoints
• Monitor for anomalous file access patterns on systems running Cisco Security Manager
• Implement network traffic analysis to identify potential exploitation attempts
• Regularly audit access logs for signs of unauthorized file access or data exfiltration

How to Mitigate CVE-2020-27130

Immediate Actions Required

• Apply the security patch provided by Cisco immediately to all affected Cisco Security Manager installations
• Restrict network access to Cisco Security Manager to only trusted administrative networks
• Implement network segmentation to limit exposure of management interfaces
• Deploy web application firewall rules to block directory traversal patterns as a temporary mitigation

Patch Information

Cisco has released a security update to address this vulnerability. Administrators should review the Cisco Security Advisory cisco-sa-csm-path-trav-NgeRnqgR for specific patch information and upgrade instructions. Organizations should upgrade to the latest version of Cisco Security Manager that addresses this vulnerability.

Workarounds

• Implement strict access control lists (ACLs) to limit which IP addresses can access the Cisco Security Manager web interface
• Deploy a reverse proxy or web application firewall configured to filter and block path traversal patterns
• Place Cisco Security Manager behind a VPN and require authentication before network access
• Monitor and log all access to Cisco Security Manager for forensic analysis

# Example ACL configuration to restrict access to Cisco Security Manager
# Apply on network perimeter or local firewall
# Allow only trusted management subnet
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP