CVE-2018-15465 in ASA
Summary
by MITRE
A vulnerability in the authorization subsystem of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, but unprivileged (levels 0 and 1), remote attacker to perform privileged actions by using the web management interface. The vulnerability is due to improper validation of user privileges when using the web management interface. An attacker could exploit this vulnerability by sending specific HTTP requests via HTTPS to an affected device as an unprivileged user. An exploit could allow the attacker to retrieve files (including the running configuration) from the device or to upload and replace software images on the device.
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Analysis
by VulDB Data Team • 06/20/2023
The vulnerability identified as CVE-2018-15465 represents a critical authorization flaw within Cisco Adaptive Security Appliance (ASA) Software that fundamentally undermines the device's security model. This issue affects the web management interface component of the ASA platform, where the authorization subsystem fails to properly validate user privileges. The vulnerability specifically targets unprivileged users operating at privilege levels 0 and 1, who should normally be restricted from performing administrative functions. However, the improper validation mechanism allows these users to escalate their privileges through crafted HTTP requests transmitted over HTTPS. The flaw exists in the web interface's privilege checking logic, where it fails to adequately verify that the requesting user possesses sufficient authorization levels before executing sensitive operations.
The technical exploitation of this vulnerability requires an authenticated attacker who has already established a session with the device's web management interface. The attacker must be at privilege level 0 or 1, which typically grants read-only access to basic device information but should not permit modification of critical system components. Through careful crafting of HTTP requests, the attacker can bypass the normal privilege validation checks that should prevent unauthorized access to privileged functions. This weakness enables the exploitation of what is essentially a privilege escalation vulnerability, where the attacker can elevate their effective privileges without requiring additional authentication credentials or elevated access rights. The vulnerability manifests through the web interface's handling of HTTP requests, where the system fails to properly validate the user's privilege level before processing administrative commands.
The operational impact of CVE-2018-15465 is severe and potentially devastating for network security infrastructure. An attacker who successfully exploits this vulnerability can perform actions that should be restricted to privileged administrators, including retrieving sensitive configuration files that may contain encryption keys, user credentials, network topology information, and other confidential data. The ability to upload and replace software images on the device creates additional risks, as it allows for complete system compromise through malicious firmware replacement. This capability enables attackers to install backdoors, modify system behavior, or completely take control of the network security appliance. The vulnerability essentially allows an attacker to perform a complete compromise of the ASA device through a web interface, bypassing traditional network security controls that should protect against such unauthorized access attempts.
Organizations affected by this vulnerability face significant risk to their network security posture, as the ASA device serves as a critical security boundary in most enterprise networks. The vulnerability's impact extends beyond simple configuration access, as the ability to upload software images creates opportunities for persistent compromise and long-term access to the network infrastructure. This flaw directly violates the principle of least privilege that should govern all network security devices, allowing unauthorized users to perform administrative functions. The security implications are particularly severe because the web management interface is often accessible from external networks, making the vulnerability exploitable from outside the organization's network perimeter. The vulnerability also demonstrates a failure in the device's defense-in-depth strategy, where multiple layers of security should have prevented such privilege escalation from occurring.
Mitigation strategies for CVE-2018-15465 should focus on immediate patching of affected Cisco ASA devices, as Cisco released security updates to address this specific vulnerability. Organizations should also implement additional network segmentation measures to limit access to ASA web management interfaces, ensuring that only authorized personnel can access these administrative functions. Network access controls should be enhanced to restrict access to the web management interface to trusted IP addresses and implement multi-factor authentication for administrative access. The principle of least privilege should be strictly enforced, with administrative access limited to the minimum necessary users and using separate administrative accounts for different functions. Regular security audits should verify that privilege levels are properly enforced and that no unauthorized access paths exist to administrative functions. This vulnerability also underscores the importance of implementing network monitoring to detect unusual access patterns or attempts to access administrative functions through web interfaces. The weakness aligns with CWE-285, which addresses improper authorization in software systems, and represents a clear violation of the ATT&CK framework's privilege escalation techniques where adversaries seek to gain elevated access rights to systems. Organizations should also consider implementing additional logging and monitoring of web interface access to detect potential exploitation attempts and maintain audit trails of administrative activities.