CVE-2024-20395: Cisco Webex Teams Info Disclosure Flaw

CVE-2024-20395 Overview

A vulnerability in the media retrieval functionality of Cisco Webex App could allow an unauthenticated, adjacent attacker to gain access to sensitive session information. This vulnerability is due to insecure transmission of requests to backend services when the app accesses embedded media, such as images. An attacker could exploit this vulnerability by sending a message with embedded media that is stored on a messaging server to a targeted user. If the attacker can observe transmitted traffic in a privileged network position, a successful exploit could allow the attacker to capture session token information from insecurely transmitted requests and possibly reuse the captured session information to take further actions as the targeted user.

Critical Impact

Adjacent network attackers can intercept session tokens transmitted insecurely when users access embedded media in Webex messages, enabling potential session hijacking and unauthorized actions as the targeted user.

Affected Products

• Cisco Webex Teams versions 3.0.x (3.0.13464.0 through 3.0.16285.0)
• Cisco Webex Teams versions 4.x (4.0 through 4.20)
• Cisco Webex Teams versions 42.x through 43.4.0.25788

Discovery Timeline

• July 17, 2024 - CVE-2024-20395 published to NVD
• July 31, 2025 - Last updated in NVD database

Technical Details for CVE-2024-20395

Vulnerability Analysis

This vulnerability represents a classic Unprotected Transport of Credentials weakness (CWE-523) within the Cisco Webex App's media handling subsystem. When users receive messages containing embedded media content such as images, the application initiates requests to backend services to retrieve and render this media. The critical flaw lies in the transmission mechanism—these requests include session token information but are sent over an insecure channel that lacks adequate encryption or protection.

The attack requires the adversary to occupy a privileged network position adjacent to the target, such as being on the same local network segment, Wi-Fi network, or having compromised intermediate network infrastructure. From this vantage point, the attacker can passively observe network traffic or actively intercept communications to capture the exposed session tokens.

Root Cause

The root cause of this vulnerability is the insecure transmission of authentication credentials during media retrieval operations. When the Webex App fetches embedded media content from messaging servers, it transmits session token information without adequate protection. This design flaw allows attackers with network visibility to intercept these tokens through passive traffic analysis or man-in-the-middle techniques.

The vulnerability specifically affects how the application handles requests to backend services for embedded content, failing to enforce secure transport mechanisms that would prevent token exposure on adjacent network segments.

Attack Vector

The attack vector requires an adjacent network position, meaning the attacker must be on the same network segment as the victim. The attack unfolds in the following manner:

1. Initial Setup: The attacker positions themselves on the same network as the target user and establishes traffic monitoring capabilities
2. Trigger Creation: The attacker sends a specially crafted message containing embedded media (such as an image) that is stored on a messaging server
3. User Interaction: When the target user views the message, the Webex App automatically attempts to retrieve the embedded media
4. Token Capture: The media retrieval request, containing session token information, is transmitted insecurely across the network
5. Session Hijacking: The attacker captures the session token from observed traffic and can reuse it to impersonate the user

This attack requires user interaction—the victim must view the malicious message containing embedded media. However, once triggered, the token exposure occurs automatically without additional user consent.

Detection Methods for CVE-2024-20395

Indicators of Compromise

• Unusual network traffic patterns involving Webex media retrieval requests containing session tokens in clear text
• Multiple authentication sessions for the same user originating from different network locations or IP addresses
• Unexpected session reuse or concurrent sessions that suggest token replay attacks
• Network logs showing media retrieval requests without expected TLS/encryption indicators

Detection Strategies

• Monitor network traffic for Webex App communications that lack proper encryption, particularly requests to backend media services
• Implement network intrusion detection rules to identify session token patterns in unencrypted HTTP traffic
• Deploy endpoint detection solutions to monitor Webex App behavior and flag anomalous media retrieval patterns
• Enable session monitoring to detect token reuse from disparate network locations

Monitoring Recommendations

• Configure SIEM alerts for multiple concurrent Webex sessions from the same user account originating from different network segments
• Implement network segmentation monitoring to detect adjacent network reconnaissance activities
• Enable detailed logging for Webex App communications at the endpoint level
• Monitor for ARP spoofing or other network positioning attacks that could enable adjacent network interception

How to Mitigate CVE-2024-20395

Immediate Actions Required

• Update Cisco Webex App to the latest patched version as specified in the vendor security advisory
• Restrict use of untrusted networks for Webex communications until patches are applied
• Implement network segmentation to limit adjacent network attack surfaces
• Enable VPN requirements for Webex usage on untrusted network segments

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory for CVE-2024-20395 for specific version information and upgrade paths. The vulnerability affects a wide range of Webex Teams versions from 3.0.13464.0 through 43.4.0.25788, requiring organizations to verify their deployed versions and plan upgrades accordingly.

Workarounds

• Enforce use of trusted, secured network connections when using Webex App for sensitive communications
• Implement 802.1X network access control to prevent unauthorized adjacent network access
• Deploy network monitoring to detect and alert on potential man-in-the-middle positioning attempts
• Consider disabling automatic media preview features until patches can be applied

# Network monitoring configuration example for detecting suspicious Webex traffic
# Configure network monitoring to detect unencrypted session tokens
# Adjust patterns based on your environment

# Example: tcpdump filter for monitoring Webex traffic on local network
tcpdump -i eth0 -n 'port 80 or port 443' and host webex.com -w webex_traffic.pcap

# Review traffic for unencrypted session token indicators
# Coordinate with security team for proper analysis