CVE-2026-76504 in Catalyst SD-WAN Manager
Summary
by MITRE • 09/30/2026
A vulnerability in the API session-based authentication management of Cisco Catalyst SD-WAN Manager could allow an unauthenticated, remote attacker to access an affected system with privileges of the admin user.
This vulnerability is due to improper handling of URI encoding in an HTTP request, which allows the request to bypass an authentication rule that is intended to restrict access to a specific API endpoint. An attacker could exploit this vulnerability by sending a crafted HTTP request to the API of the affected system. A successful exploit could allow the attacker to bypass authentication and gain access to the API as the admin user.
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Analysis
by VulDB Data Team • 09/30/2026
The Cisco Catalyst SD-WAN Manager, a critical component in software-defined wide area network architectures, manages centralized configuration, policy enforcement, and monitoring for distributed branch offices and data centers. The security of this management plane is paramount because compromise can lead to widespread network disruption or unauthorized control over enterprise traffic flows. A significant vulnerability has been identified within the API session-based authentication mechanism that governs access to these administrative functions. This flaw stems from an improper handling of Uniform Resource Identifier encoding during HTTP request processing, which creates a bypass vector for authentication controls designed to restrict access to specific application programming interface endpoints.
The technical root cause lies in how the system parses and validates URI parameters against defined security policies. When an attacker crafts an HTTP request with specifically encoded characters or malformed URIs, the underlying parsing logic fails to correctly interpret the intended path structure relative to the authentication ruleset. This discrepancy allows the malicious request to slip past the gateway checks that normally require valid administrative credentials before granting access to sensitive API endpoints. Instead of rejecting the unauthenticated attempt as expected, the system processes the request and grants it the privileges associated with an administrator account due to this logic error in input validation and path resolution.
From a threat modeling perspective, this vulnerability aligns closely with CWE-79 Improper Neutralization of Input During Web Page Generation or more specifically CWE-200 Exposure of Sensitive Information Through Discretionary Access Control when considering the bypass aspect, but most accurately maps to CWE-345 Insufficient Verification of Data Authenticity and CWE-613 Insufficient Session Expiration. In terms of offensive security frameworks such as MITRE ATT&CK, this exploitation technique falls under T1078 Valid Accounts, specifically leveraging valid administrative credentials through bypass mechanisms rather than credential theft. It also relates to T1190 Exploit Public-Facing Application, where the attacker leverages a flaw in an internet-facing service to gain initial access.
The operational impact of successfully exploiting this vulnerability is severe and immediate. An unauthenticated remote attacker can execute arbitrary commands or modify configurations on the SD-WAN Manager without any prior authentication. This effectively grants full administrative control over the entire software-defined network infrastructure. Attackers could manipulate routing policies, intercept traffic through man-in-the-middle attacks enabled by policy changes, deploy malware across branch offices via configuration pushes, or exfiltrate sensitive data stored within the management plane. The ability to bypass authentication entirely removes a fundamental layer of defense in depth, turning what should be an authenticated administrative interface into an open door for remote code execution and network takeover.
Mitigation strategies must address both immediate remediation and long-term architectural resilience. Cisco has released software updates that patch this specific URI encoding flaw by enforcing stricter validation rules on incoming HTTP requests before they reach the authentication module. Administrators are strongly advised to apply these patches immediately upon availability. In environments where patching is not instantly feasible, network segmentation should be implemented to ensure the SD-WAN Manager API endpoints are only accessible from trusted management subnets rather than exposed directly to untrusted networks like the internet. Additionally, implementing Web Application Firewalls with rules capable of detecting and blocking anomalous URI encoding patterns can provide a temporary compensating control by filtering out requests that exhibit characteristics typical of this specific bypass technique before they reach the application layer.