CVE-2026-76413 in Secure Firewall Management Center
Summary
by MITRE • 09/16/2026
A vulnerability in Cisco Adaptive Security Device Manager (ASDM) single sign-on (SSO) handler for Cisco Secure FMC Software could allow an unauthenticated, remote attacker to log in as the Cisco ASDM administrator user.
This vulnerability is due to improper management of the Cisco ASDM SSO token. An attacker could exploit this vulnerability by performing session token forgery techniques. A successful exploit could allow the attacker to log in as the administrator user and, by repeating this action, keep legitimate administrators locked out of the ASDM indefinitely.
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Analysis
by VulDB Data Team • 09/16/2026
The identified security flaw resides within the Cisco Adaptive Security Device Manager single sign-on handler component of Cisco Secure FMC Software, presenting a critical risk to network infrastructure management interfaces. This vulnerability stems from an improper implementation and validation mechanism for session tokens used in the authentication process. Specifically, the system fails to adequately verify the integrity or origin of these tokens during the SSO handshake, allowing external actors to bypass standard authentication protocols. The core technical deficiency lies in the lack of robust cryptographic verification or state management checks that would normally ensure a token was legitimately issued by an authorized identity provider and has not been tampered with. This architectural oversight creates a direct pathway for session hijacking or impersonation attacks against administrative accounts.
An unauthenticated, remote attacker can exploit this weakness by crafting forged SSO tokens that mimic valid authentication credentials. By manipulating the request parameters to include these maliciously constructed tokens, the attacker can trick the ASDM interface into granting access without requiring valid user credentials. This capability effectively neutralizes the primary defense mechanism of the management plane, allowing unauthorized individuals to assume the role of the Cisco ASDM administrator. The exploit does not require prior authentication or physical proximity to the network device, making it a high-severity remote code execution vector in terms of administrative control rather than direct system command injection.
The operational impact of this vulnerability is severe due to its potential for persistent unauthorized access and denial of service against legitimate administrators. Once an attacker successfully logs in as the administrator using the forged token, they gain full control over the security management platform. This level of access enables the modification of firewall policies, inspection rules, and network configurations, potentially leading to data exfiltration, lateral movement within the enterprise network, or complete disruption of security services. Furthermore, by repeatedly exploiting this flaw, an attacker can maintain continuous administrative presence while simultaneously locking out legitimate administrators. This lockout effect ensures that defenders cannot easily remediate the breach through standard interface access, complicating incident response and recovery efforts significantly.
From a classification perspective, this vulnerability aligns with CWE-287, which denotes Improper Authentication, specifically regarding the failure to properly validate credentials or tokens during the authentication process. It also maps closely to MITRE ATT&CK technique T1078, Valid Accounts, where adversaries use legitimate account credentials to gain access to systems and evade detection by appearing as normal users. The specific method of token forgery relates to CWE-345, Insufficient Verification of Data Authenticity, highlighting the failure in verifying that the session data originated from a trusted source.
Mitigation strategies must focus on immediate patching and enhanced monitoring until updates are applied. Organizations should apply the latest software patches released by Cisco for their Secure FMC appliances to address the token validation logic flaws. In environments where patching is not immediately feasible, network segmentation controls should be enforced to restrict access to the ASDM management interface exclusively from trusted IP addresses or jump hosts. Additionally, implementing strict logging and alerting on administrative login attempts can help detect anomalous activity indicative of this exploitation attempt. Security teams should monitor for unusual patterns in session token usage and ensure that multi-factor authentication is enabled wherever supported by the platform version to add an additional layer of verification beyond simple token validation.