CVE-2026-20056
Unknown Unknown - Not Provided
Anti-Malware Bypass in Cisco AsyncOS DVS Engine

Publication date: 2026-02-04

Last updated on: 2026-02-04

Assigner: Cisco Systems, Inc.

Description
A vulnerability in the Dynamic Vectoring and Streaming (DVS) Engine implementation of Cisco AsyncOS Software for Cisco Secure Web Appliance could allow an unauthenticated, remote attacker to bypass the anti-malware scanner, allowing malicious archive files to be downloaded. This vulnerability is due to improper handling of certain archive files. An attacker could exploit this vulnerability by sending a crafted archive file, which should be blocked, through an affected device. A successful exploit could allow the attacker to bypass the anti-malware scanner and download malware onto an end user workstation. The downloaded malware will not automatically execute unless the end user extracts and launches the malicious file. 
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Meta Information
Published
2026-02-04
Last Modified
2026-02-04
Generated
2026-06-16
AI Q&A
2026-02-04
EPSS Evaluated
2026-06-15
NVD
CVE-2026-20056
EUVD
EUVD-2026-5425
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
cisco asyncos *
cisco asyncos 15.2.5-011
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-494 The product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code.
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Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-20056 is a medium-severity vulnerability in the Dynamic Vectoring and Streaming (DVS) Engine of Cisco AsyncOS Software for Cisco Secure Web Appliance. It occurs because the software improperly handles certain archive files.'}, {'type': 'paragraph', 'content': "An unauthenticated, remote attacker can exploit this by sending specially crafted archive files that should be blocked by the anti-malware scanner. This allows the attacker to bypass the scanner and download malicious archive files onto an end user's workstation."}, {'type': 'paragraph', 'content': 'However, the malware will not execute automatically; it requires the user to manually extract and launch the malicious content.'}] [1]

Impact Analysis

This vulnerability can impact you by allowing an attacker to bypass the anti-malware protections of the Cisco Secure Web Appliance and deliver malicious archive files to your workstation.

If a user extracts and launches the malicious files, malware could be installed on the workstation, potentially compromising the system.

There are no workarounds available, so the only way to mitigate this risk is to upgrade to the fixed software versions provided by Cisco.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

To mitigate this vulnerability, Cisco advises all users to upgrade to the fixed software versions. The first fixed release addressing this issue is AsyncOS 15.2.5-011.

Upgrades can be performed via the appliance’s web interface using the System Upgrade options.

There are no workarounds available for this vulnerability, so applying the fixed software is the only effective mitigation.

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