Critical Cisco Webex Flaw Allows Code Execution via Malicious Meeting Links

A critical vulnerability (CVE-2025-20236) in Cisco Webex App’s custom URL parser has been patched, addressing a high-severity flaw that allows unauthenticated attackers to execute arbitrary commands on targeted systems.

With a CVSSv3.1 score of 8.8, this client-side remote code execution (RCE) vulnerability poses significant risks to organizations using Webex for collaboration.

Risk Factor Overview

Technical Overview

The vulnerability (CWE-829) stems from insufficient input validation in Webex App’s URL parsing mechanism when processing meeting invite links.

Attackers can craft malicious links that, when clicked, trigger the download of arbitrary files.

These files may then execute commands with the privileges of the targeted user, enabling:

• Unauthorized system access
• Data exfiltration
• Lateral movement within networks

The exploit leverages Webex’s handling of meetingURL parameters, where malformed input bypasses security checks.

For example, a link like webex://meet?url=<malicious_payload> could inject executable code into the host system.

Exploitation Mechanics

• Attack Vector: Network-based, requiring user interaction (clicking a link).
• CVSSv3.1 Breakdown:
  • Attack Vector (AV): Network (N)
  • Attack Complexity (AC): Low (L)
  • Privileges Required (PR): None (N)
  • User Interaction (UI): Required (R)
  • Impact Metrics: High (H) confidentiality, integrity, and availability compromises.

Cisco confirmed the flaw during internal security testing, with no evidence of public exploits or active attacks as of April 16, 2025.

However, the absence of workarounds elevates the urgency for patching.

Mitigation and Remediation

Cisco has released updates for affected versions:

• 44.6.x users: Upgrade to 44.6.2.30589.
• 44.7.x users: Migrate to version 44.8 or later.

Recommended Actions:

1. Immediate Patching: Deploy fixed releases via Cisco’s standard update channels.
2. User Awareness Training: Educate employees on the risks of unsolicited meeting links.
3. Network Filtering: Block suspicious URLs and monitor for anomalous traffic patterns.
4. Endpoint Protection: Enable behavior-based threat detection to identify exploit attempts.

Advisory Details

• Advisory ID: cisco-sa-webex-app-client-rce-ufyMMYLC
• Cisco Bug ID: CSCwn07296
• Advisory Link: Cisco Security Advisory

Broader Implications

This vulnerability highlights the growing threat landscape targeting collaboration tools.

Unlike server-side flaws, client-side RCE exploits often bypass perimeter defenses, relying on social engineering to succeed.

The Webex flaw’s high CVSS score reflects its potential for widespread impact, particularly in enterprises where the app is deeply integrated into workflows.

Cisco’s prompt patch release aligns with its PSIRT protocols, but administrators must prioritize updates given the lack of mitigations.

Organizations should also audit logs for unusual meeting link activity and consider segmenting networks to limit lateral movement post-exploitation.

CVE-2025-20236 underscores the critical need for rigorous input validation in software handling user-provided URLs.

As hybrid work models expand, securing communication platforms against client-side attacks remains paramount.

Cisco users should treat this vulnerability as a top-priority remediation item to prevent potential breaches.

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