CVE-2021-1242 in WebEx Teams
Summary
by MITRE • 01/14/2021
A vulnerability in Cisco Webex Teams could allow an unauthenticated, remote attacker to manipulate file names within the messaging interface. The vulnerability exists because the affected software mishandles character rendering. An attacker could exploit this vulnerability by sharing a file within the application interface. A successful exploit could allow the attacker to modify how the shared file name displays within the interface, which could allow the attacker to conduct phishing or spoofing attacks.
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Analysis
by VulDB Data Team • 02/14/2021
This vulnerability resides within Cisco Webex Teams messaging platform where improper handling of character rendering creates a security weakness that can be exploited by unauthenticated remote attackers. The flaw specifically manifests when the application processes and displays file names within its user interface, allowing attackers to manipulate how filenames appear to end users. The vulnerability stems from inadequate input validation and sanitization mechanisms that fail to properly process special characters and rendering sequences, creating an opportunity for attackers to craft deceptive file names that could mislead users about the actual content or source of shared files.
The technical exploitation of CVE-2021-1242 occurs through the application's file sharing functionality where attackers can craft malicious filenames containing specific character sequences that alter the visual representation of the file name in the messaging interface. This character rendering manipulation allows attackers to create file names that appear legitimate while actually containing malicious elements or misleading information. The vulnerability is classified under CWE-74 as a "Improper Neutralization of Special Elements in Output Used by a Downstream Component" and aligns with ATT&CK technique T1566.001 for "Phishing: Spearphishing Attachment" where the manipulated file names serve as a vector for social engineering attacks. Attackers can leverage this weakness to create file names that disguise malicious payloads as benign documents, potentially bypassing user suspicion and security awareness.
The operational impact of this vulnerability extends beyond simple visual manipulation to enable sophisticated phishing and spoofing campaigns within the Webex Teams environment. Users may be misled into opening malicious files believing them to be legitimate documents from trusted sources, as the manipulated display makes it difficult to distinguish between authentic and forged file names. This creates a significant risk for organizations relying on Webex Teams for business communications, as the vulnerability can be exploited across various file types including documents, images, and executables. The attack surface includes any user interaction with shared files within the messaging interface, potentially affecting thousands of users in enterprise environments where Webex Teams is widely deployed. The vulnerability particularly impacts organizations with limited security awareness training, as users may not recognize the subtle visual manipulations that occur in the file display.
Mitigation strategies for CVE-2021-1242 should focus on both immediate patching and operational security improvements. Cisco has released software updates addressing this vulnerability, and organizations must prioritize deployment of the latest Webex Teams client versions and server-side patches. Network administrators should implement additional monitoring for suspicious file sharing activities and consider implementing file type restrictions or content scanning for shared files. Security teams should conduct user awareness training specifically addressing the risks of visual deception in messaging platforms, emphasizing that file names may be manipulated. Organizations should also consider implementing application whitelisting policies to restrict execution of unknown file types and establish clear protocols for verifying file authenticity before opening shared documents. The vulnerability highlights the importance of proper input validation and output encoding in web applications, particularly in collaborative environments where users share files and information regularly.