External risk intelligence

IBM Sterling File Gateway Improper Authentication Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-75878

IBM Sterling File Gateway is an enterprise solution designed to manage and facilitate the transfer of files between organizations. It is typically deployed as a public-facing gateway or edge service to allow external partners and clients to connect, making it inherently internet-facing by design.

Authentication Bypass

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

IBM Sterling File Gateway has a critical vulnerability that could allow unauthorized access to authenticated sessions by bypassing authentication checks. This impacts systems handling file transfers, potentially exposing sensitive data or operations. The main concern is confirming if our environment is affected and understanding the potential exposure.

Improper authentication allows unauthorized access.
Affects critical file transfer gateway technology.
Confirm relevance and potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending a specially crafted request to IBM Sterling File Gateway. This request would leverage an unvalidated Single Sign-On (SSO) header to bypass the normal authentication process. Successful exploitation would allow the attacker to obtain a fully authenticated session, granting them access as if they had legitimately logged in.

No authentication required to initiate.
Unvalidated SSO header triggers vulnerability.
Full authentication bypass.

Live Threat

Current exploitation, exposure, and threat context

A remote attacker could bypass authentication to gain a fully authenticated session in IBM Sterling File Gateway. This could occur when the system improperly validates an SSO header, potentially exposing sensitive information or allowing unauthorized actions when supported by the advisory.

System access.
Unvalidated SSO header.
Unauthorized session access.

Operational Fix

Recommended remediation, mitigation, and detection steps

IBM Sterling File Gateway, a solution for managing file transfers between organizations, is susceptible to an unvalidated SSO header vulnerability, potentially allowing remote attackers to bypass authentication. Responsibility for addressing this issue likely falls to the platform or infrastructure teams managing the Sterling gateway, in coordination with the application owners and potentially the vendor-management team if a third-party solution is involved. The immediate first step is to identify all instances of Sterling File Gateway, confirm their accessibility from the internet or sensitive internal networks, and determine the business criticality of each deployment to prioritize remediation efforts.

Platform and application owners should lead.
Verify external and internal exposure.
Plan remediation based on business risk.

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 IBM Sterling File Gateway?

IBM Sterling File Gateway is an enterprise software solution used by organizations to manage, automate, and secure the exchange of large volumes of files with external partners, clients, or internal systems. It functions as a centralized hub to ensure data delivery across different protocols and networks, often acting as a critical bridge for business-to-business communications.

What does CVE-2026-75878 mean?

This vulnerability, classified as CWE-287 (Improper Authentication), means the software fails to verify the identity of a user correctly. Specifically, it allows an attacker to bypass the login process entirely by exploiting an unvalidated Single Sign-On (SSO) header. By manipulating this header, the system is tricked into granting an attacker a fully authenticated session as if they had successfully provided valid credentials.

How is this authentication bypass triggered?

The flaw is triggered when an attacker sends a specially crafted network request that contains an unvalidated SSO header. The system incorrectly trusts this header and assumes the user is already authenticated. Note that standard, correctly validated login requests that do not involve manipulated SSO headers do not trigger this vulnerability.

Do I need to worry if my system is internet-facing?

Yes, high priority is recommended. According to Halo Surface Signal, IBM Sterling File Gateway is typically deployed as a public-facing edge service to facilitate external connections, which often places it directly on the internet. If your instance is exposed to the internet, it is reachable by remote attackers who can attempt to inject the malicious SSO header without needing prior access or credentials.

What should I do first to address this?

Start by conducting an inventory to locate all instances of IBM Sterling File Gateway within your infrastructure. Once identified, evaluate the network accessibility of each instance—specifically checking if they are reachable from the internet—and assess the business criticality of the data they handle. This information helps you prioritize which systems to secure first while you await official guidance or updates from the vendor.

References

www.ibm.com/support/pages/node/7287497

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.