Cisco Firepower Extensible Operating System cross site scripting

Summaryinfo

A vulnerability has been found in Cisco Firepower Extensible Operating System, Secure Firewall Adaptive Security Appliance Software and Unified Computing System and classified as problematic. The impacted element is an unknown function. Performing a manipulation results in cross site scripting. This vulnerability is known as CVE-2026-20091. Remote exploitation of the attack is possible. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as problematic has been found in Cisco Firepower Extensible Operating System, Secure Firewall Adaptive Security Appliance Software and Unified Computing System (the affected version unknown). This affects an unknown part. The manipulation with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. The summary by CVE is:

A vulnerability in the web-based management interface of Cisco FXOS Software and Cisco UCS Manager Software could allow an authenticated, remote attacker to conduct a stored cross-site scripting (XSS) attack against a user of the interface. This vulnerability is due to insufficient validation of user-supplied input by the web-based management interface of an affected system. An attacker could exploit this vulnerability by injecting malicious data into specific pages of the interface. A successful exploit could allow the attacker to execute arbitrary script code in the context of the affected interface or access sensitive, browser-based information. To exploit this vulnerability, the attacker must have valid credentials for a user account with the role of Administrator or AAA Administrator. 

The advisory is shared at sec.cloudapps.cisco.com. This vulnerability is uniquely identified as CVE-2026-20091 since 10/08/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. The exploitation requires an enhanced level of successful authentication. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 02/28/2026). MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

Upgrading eliminates this vulnerability.

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Productinfo

Type

• Virtualization Software

Vendor

• Cisco

Name

• Firepower Extensible Operating System
• Secure Firewall Adaptive Security Appliance Software
• Unified Computing System

License

• commercial

Website

• Vendor: https://www.cisco.com/

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