External risk intelligence

SSO Master Password Bypass Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-79577

The vulnerability exists in the /cas/login component of an SSO (Single Sign-On) application. SSO solutions are identity portals designed by nature to be public-facing to facilitate user authentication for web services, making them highly likely to be exposed to the internet.

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns a critical vulnerability found in the authentication component of an SSO (Single Sign-On) system, specifically within the login process. The flaw enables unauthorized access without requiring credentials, which could potentially impact systems relying on this SSO for user management and access control. The primary concern is to confirm if this specific SSO technology is in use and, if so, to understand its exposure.

Unauthenticated access to a single sign-on system.
High impact if identity management is compromised.
Verify usage and exposure of this SSO technology.

Attack Path

How an attacker could exploit the issue

An attacker can bypass password authentication by sending a specially crafted POST request to the `/cas/login` component. This allows them to gain unauthorized access to the application.

Open network access
Send crafted POST request
Unauthorized access to application

Live Threat

Current exploitation, exposure, and threat context

The `/cas/login` component in sso-master may allow attackers to authenticate without a password by sending a specially crafted POST request. This could potentially expose system data, user data, and service behavior when the application is accessible over the network and configured to handle authentication requests.

System authentication data at risk.
Authentication bypass via crafted POST requests.
Unauthorized access to application functions.

Operational Fix

Recommended remediation, mitigation, and detection steps

The critical vulnerability in the SSO login component requires immediate attention from application owners and infrastructure teams responsible for the SSO solution. The first step is to identify all instances of the affected SSO technology, confirm its external reachability, and determine its business criticality. Once confirmed, engage the accountable owner to prioritize and plan remediation, coordinating with the vendor if necessary.

Application and infrastructure teams own remediation.
Verify SSO reachability and criticality first.
Plan vendor-coordinated patch or mitigation.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is sso-master and how is it used?

sso-master is a Single Sign-On software package designed to centralize identity management. It serves as an authentication gateway, allowing users to log in once to gain access to multiple connected web services or applications, effectively acting as the front door for user verification across a digital environment.

What does CWE-284 mean in the context of CVE-2026-79577?

CWE-284 refers to Improper Access Control. In this vulnerability, it means the application fails to properly enforce restrictions on who can access its resources. Specifically, the software's login mechanism does not correctly verify credentials, allowing a user to bypass the password requirement entirely and gain unauthorized entry to the system.

How does an attacker trigger this authentication bypass?

An attacker triggers the vulnerability by sending a specifically crafted POST request directly to the /cas/login component. The bug is specifically tied to how this endpoint processes incoming data; it is not triggered by standard web navigation or simple page loads, but requires this structured request to manipulate the authentication logic.

Why should I be concerned if my sso-master instance is internet-facing?

Halo Surface Signal notes that SSO solutions are inherently designed to be public-facing to support remote users. Because this vulnerability allows unauthenticated access via the network, any instance reachable from the internet is at high risk, as attackers do not need to be on your local network to exploit the authentication flaw.

How should I respond if I use sso-master?

Begin by auditing your infrastructure to locate all instances of sso-master v1.0.0. Once identified, assess whether they are reachable over the network and determine their importance to your business operations. Engage your technical team to prioritize these assets for remediation and coordinate with the software vendor for available patches or mitigation steps.

References

github.com/fangtang7/CVE/blob/main/sso-master/sso.md

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.