Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to bypass security restrictions on an affected system.
This vulnerability is due to an error within the Cisco IOS Software authentication proxy feature. An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious request to the affected system. If successful, the attacker could bypass proxy security protections and access protected resources.
Cisco has confirmed this vulnerability in a security advisory and released software updates.
Indicators of Compromise
Cisco has published a list of affected Cisco IOS Software releases in the security advisory. The Vendor Announcements section of this alert contains a link to the advisory.
This vulnerability is due to an error within the Cisco IOS Software authentication proxy feature. A race condition exists when processing requests to the proxy. The proxy feature may start additional sessions without properly requesting authentication from new connections, allowing access to the proxy without authentication.
An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious request to the affected system. Another active proxy session must be active. If an exploit is successful, the attacker could establish a proxy session with the privileges of another user. This action could allow the attacker to access restricted resources.
To exploit this vulnerability, an attacker must have access to trusted, internal networks. Additionally, the attacker cannot exploit this vulnerability until another user establishes an active session with the targeted proxy. Because of a race condition, exploitation may not be reliable. The access requirements greatly limit the potential for exploitation.
An exploit could allow an attacker to bypass proxy security settings and access protected segments of the network. As a result, the attacker could make outgoing connections to external networks, potentially resulting in unauthorized data transmissions. The attacker could also access resources such as internal web services that are protected by a proxy server.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
Administrators are advised to apply the appropriate update.
Administrators are advised to restrict network access to affected systems.
Administrators are advised to monitor critical systems.
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 e-mail at firstname.lastname@example.org.
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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.