CVE-2022-20791: Cisco Unified CM Information Disclosure

CVE-2022-20791 Overview

A path traversal vulnerability exists in the database user privileges of Cisco Unified Communications Manager (Unified CM), Cisco Unified Communications Manager Session Management Edition (Unified CM SME), and Cisco Unified Communications Manager IM & Presence Service (Unified CM IM&P). This vulnerability could allow an authenticated, remote attacker to read arbitrary files on the underlying operating system of an affected device. The vulnerability stems from insufficient file permission restrictions, enabling attackers with valid user credentials to send crafted commands via the API to access sensitive system files.

Critical Impact

Authenticated attackers can read arbitrary files from the underlying operating system, potentially exposing sensitive configuration data, credentials, and system information from affected Cisco Unified Communications infrastructure.

Affected Products

• Cisco Unified Communications Manager (Unified CM)
• Cisco Unified Communications Manager Session Management Edition (Unified CM SME)
• Cisco Unified Communications Manager IM & Presence Service (Unified CM IM&P)

Discovery Timeline

• 2022-07-06 - CVE CVE-2022-20791 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-20791

Vulnerability Analysis

This vulnerability is classified under CWE-22 (Improper Limitation of a Pathname to a Restricted Directory, Path Traversal) and CWE-36 (Absolute Path Traversal). The root issue lies in how the Cisco Unified Communications Manager handles file access requests through its API. Due to insufficient file permission restrictions on database user privileges, the application fails to properly validate and sanitize file path inputs submitted through API commands.

An attacker who has obtained valid user credentials can leverage this weakness to traverse outside of intended directories and access arbitrary files on the underlying operating system. The network-accessible nature of this vulnerability combined with low attack complexity makes it particularly concerning for organizations running exposed Unified Communications infrastructure. While the vulnerability requires authentication, the ability to read arbitrary system files could lead to secondary compromise through credential theft or configuration disclosure.

Root Cause

The vulnerability is caused by insufficient file permission restrictions in the database user privileges implementation. The application does not adequately restrict which files authenticated database users can access through API commands, allowing path traversal sequences to escape the intended directory structure and access files elsewhere on the operating system.

Attack Vector

The attack is conducted over the network and requires valid user credentials. An attacker sends a specially crafted command through the API that includes path traversal sequences (such as ../) or absolute paths to target files outside the application's intended scope. The crafted request bypasses file permission checks, and the application returns the contents of the requested file to the attacker.

The vulnerability exploitation flow involves:

1. The attacker authenticates to the Cisco Unified CM API using valid credentials
2. A malicious API request is crafted containing path traversal sequences targeting sensitive system files
3. The application fails to properly validate the file path against permission restrictions
4. The contents of the arbitrary file are returned to the attacker

Detection Methods for CVE-2022-20791

Indicators of Compromise

• Unusual API requests containing path traversal sequences (../, ..\\) or references to system configuration files
• Anomalous database user activity accessing files outside normal operational scope
• API access logs showing repeated attempts to access sensitive system paths like /etc/passwd, /etc/shadow, or application configuration files
• Authenticated sessions exhibiting reconnaissance behavior across multiple file paths

Detection Strategies

• Monitor Cisco Unified CM API logs for requests containing path traversal patterns or absolute file paths
• Implement file integrity monitoring on sensitive operating system files to detect unauthorized read attempts
• Configure SIEM rules to alert on unusual patterns of file access through the API from authenticated users
• Deploy network traffic analysis to identify API requests with suspicious path patterns

Monitoring Recommendations

• Enable detailed API request logging on all Cisco Unified Communications Manager instances
• Review authentication logs for unusual login patterns or credential abuse that may precede exploitation
• Monitor for lateral movement following potential file disclosure, especially attempts to use harvested credentials
• Establish baseline API usage patterns to detect anomalous file access behavior

How to Mitigate CVE-2022-20791

Immediate Actions Required

• Apply the security patches provided by Cisco immediately to all affected Unified Communications Manager deployments
• Review and restrict API access permissions to the minimum necessary for operational requirements
• Audit user credentials with API access and enforce strong authentication controls
• Implement network segmentation to limit exposure of Unified CM management interfaces

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory for specific patch versions and installation instructions for their affected products. The advisory provides detailed information on fixed software releases for Cisco Unified Communications Manager, Unified CM SME, and Unified CM IM&P.

Workarounds

• Restrict network access to Cisco Unified CM administration and API interfaces using firewall rules and ACLs
• Implement strong authentication mechanisms including multi-factor authentication for administrative access
• Monitor and audit all API access activity with enhanced logging until patches can be applied
• Review and minimize the number of user accounts with API privileges