A vulnerability in the WebVPN login page of Cisco Adaptive Security
Appliance (ASA) Software could allow an unauthenticated, remote attacker
to conduct a cross-site scripting (XSS) attack against a user of WebVPN
on the Cisco ASA.
The vulnerability is due to insufficient input
validation of a parameter. An attacker could exploit this vulnerability
by convincing a user to access a malicious link.
Cisco PSIRT would like to thank Piotr Karolak of Trustwave's SpiderLabs for reporting this vulnerability.
Cisco has confirmed the vulnerability and released software updates.
Indicators of Compromise
Cisco ASA Software versions 8.4(7) and prior and 9.1(4) and prior are vulnerable.
The vulnerability is due to insufficient input validation of a parameter by the affected software.
An unauthenticated, remote attacker could exploit this vulnerability by convincing a user to access a malicious link. If successful, the attacker could execute arbitrary script code in the user's browser session and steal sensitive information, such as authentication cookies.
To exploit the vulnerability, the attacker may provide a link that directs a user to a malicious site and use misleading language or instructions to persuade the user to follow the provided link.
Cisco indicates through the CVSS score that proof-of-concept exploit code exists; however, the code is not known to be publicly available.
Administrators are advised to apply the appropriate updates.
Users are advised not to open email messages from suspicious or unrecognized sources. If users cannot verify that links or attachments included in email messages are safe, they are advised not to open them.
Administrators are advised to monitor affected systems.
Customers are advised to consult Cisco bug ID CSCun19025 for a complete list of affected and fixed product versions.
Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via email at email@example.com.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.