CVE-2026-76731 in Instant On
Summary
by MITRE • 09/29/2026
An authentication bypass vulnerability in the captive portal of HPE Networking Instant On could allow an unauthenticated remote attacker to circumvent existing authentication controls. Successful exploitation could allow an attacker to gain limited access to some data and to make limited changes within the affected component.
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Analysis
by VulDB Data Team • 09/29/2026
The identified security flaw resides within the captive portal implementation of Hewlett Packard Enterprise Networking Instant On devices, representing a critical failure in identity verification mechanisms. This vulnerability allows unauthenticated remote attackers to bypass standard authentication controls that are typically required before granting network access or administrative privileges. The root cause lies in how the web server and associated application logic handle session states and credential validation during the initial connection phase. Specifically, the system fails to properly enforce mandatory checks for valid user credentials or active sessions when processing specific requests directed at sensitive endpoints within the captive portal interface. This architectural oversight creates a pathway where an attacker can interact with internal services without first proving their identity through legitimate means such as username and password entry or certificate validation.
From a technical perspective, this issue aligns closely with CWE-287, which describes Improper Authentication, and more specifically reflects the characteristics of CWE-306, Missing Authentication for Critical Function. The vulnerability exploits the gap between network-level access control and application-layer authentication requirements. By manipulating HTTP requests or exploiting race conditions in session management, an attacker can trick the captive portal into treating unauthenticated traffic as authorized. This bypass is particularly dangerous because it occurs at a layer that users often perceive as secure due to its role in gateway security. The flaw does not necessarily require complex exploitation techniques but rather precise request crafting to trigger the authentication logic failure, allowing direct interaction with backend services or configuration interfaces that should remain restricted.
The operational impact of this vulnerability is significant for organizations relying on HPE Instant On infrastructure for network segmentation and user access management. Successful exploitation enables an attacker to gain limited but potentially damaging access to internal data resources. This may include viewing sensitive information such as connected device lists, network topology details, or cached configuration snippets that are not intended for public consumption. Furthermore, the ability to make limited changes within the affected component means an attacker could alter basic settings, redirect traffic, or disrupt service availability by modifying captive portal parameters. While full administrative control might require additional privileges, this level of access is sufficient for reconnaissance, data exfiltration on a small scale, and establishing a foothold for further lateral movement within the network environment.
This vulnerability maps directly to MITRE ATT&CK technique T1078, Valid Accounts, as it effectively allows an attacker to operate with valid session privileges without possessing actual credentials. It also relates to T1190, Exploit Public-Facing Application, given that the captive portal is often exposed to untrusted networks or internet-facing interfaces depending on deployment configuration. The ability to bypass authentication controls undermines the fundamental principle of least privilege and compromises the integrity of the network access control strategy employed by the organization.
To mitigate this risk, immediate action should be taken to apply vendor-provided patches that address the specific logic flaws in the captive portal authentication module. Administrators must ensure all affected devices are updated to the latest stable firmware version released by HPE Networking. In environments where patching is not immediately feasible, network segmentation strategies can help isolate vulnerable components from critical data stores and management planes. Additionally, implementing strict access control lists on firewall rules to restrict direct HTTP/HTTPS traffic to the captive portal interfaces only from trusted subnets can reduce the attack surface. Regular auditing of authentication logs for anomalous patterns indicative of bypass attempts is also recommended to detect potential exploitation in real-time.