Summary
CVE-2026-75878 is a critical authentication bypass vulnerability in IBM Sterling File Gateway. The flaw stems from improper authentication handling of an unvalidated SSO (Single Sign-On) header, allowing a remote, unauthenticated attacker to obtain a fully authenticated session. IBM rates the issue 9.1 (Critical) on CVSS v3.1.
Technical details
- Root cause: Sterling File Gateway’s authentication logic accepts an SSO-related HTTP header value without properly validating it, treating attacker-supplied header content as proof of a legitimate authenticated identity.
- Trigger conditions: An attacker sends a crafted HTTP request containing a forged/unvalidated SSO header to a reachable Sterling File Gateway instance; no prior authentication, user interaction, or special privileges are required.
- Attack vector: Network — the vulnerable interface is exposed over HTTP(S) and exploitable remotely without local access.
- Impact: Successful exploitation grants the attacker a fully authenticated session, resulting in high confidentiality and high integrity impact (unauthorized access to and potential manipulation of data/functionality available to authenticated users). Availability is not impacted.
- Classified as CWE-287 (Improper Authentication).
Affected software
- IBM Sterling File Gateway 6.2.0.0 through 6.2.0.6_1
- IBM Sterling File Gateway 6.2.1.0 through 6.2.1.2
- IBM Sterling File Gateway 6.2.2.0 through 6.2.2.1
Severity
- CVSS v3.1 Base Score: 9.1 (Critical)
- Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Mitigation and recommended actions
- Immediate: Upgrade to the fixed releases published by IBM:
- 6.2.0.6_2 (for the 6.2.0.x line)
- 6.2.1.2_1 (for the 6.2.1.x line)
- 6.2.2.1_1 (for the 6.2.2.x line)
- Fixes are available via IBM Fix Central for on-prem installations and via the IBM Entitled Registry (
cp.icr.io/cp/ibm-sfg) for container deployments; for 6.2.0.6_2 contact IBM Support directly.
- If no patch can be applied immediately: IBM states no workarounds are currently available for this vulnerability, so patching is the only effective remediation. Organizations unable to patch immediately should restrict network exposure of Sterling File Gateway management/authentication interfaces to trusted networks until the fix is applied.

