CVE-2026-48558

SimpleHelp contains an authentication bypass vulnerability in the OIDC authentication flow. When OIDC authentication is configured, identity tokens submitted during login are accepted without verifying their cryptographic signature. In a vulnerable configuration, a remote, unauthenticated attacker can submit a forged token containing arbitrary identity claims to obtain a fully authenticated technician session. In some configurations, this may also allow bypass of multi-factor authentication.

What this means for your business

It affects SimpleHelp. It matters if your company, or a supplier that handles your data, runs it.
Attackers are already using it. CISA added it to its list of flaws used in real attacks on 29 June 2026.
An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
FIRST's prediction model gives it a 78% chance of attack attempts being seen in the next 30 days, ranking above 99% of all known flaws.

What to do

1Check whether your company or your suppliers run SimpleHelp, and which version. The affected versions are listed further down this page.
2If you do, apply the vendor's fix. A patch or vendor advisory has been published.
3Treat it as urgent. US federal agencies must fix it by 2 July 2026. That deadline does not apply to private companies, but it shows how seriously CISA takes it.
4Because attackers have used it, check the affected systems for signs of a break-in, not only for the update.

Fastnexa security experts

Attackers are already using this flaw. Is your SimpleHelp SimpleHelp exposed?

Tell us where you run SimpleHelp SimpleHelp and a Fastnexa penetration tester will check whether this flaw, or others like it, can be used against your websites, apps and network.

The full test is free for our first 10 founding clients until 31 December 2026. See the offer

Book a 30-min call WhatsApp us

Think you’ve already been hit? Don’t wait on a form: call or WhatsApp +1 (732) 454 2616. We reply within 1 hour, 24/7. Emergency help →

Required action

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

CISA’s wording, unedited. The notes it mentions are in CISA’s catalogue entry.

Scoring

CVSS: 10.0 (v3.1)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CVSS v4: 9.5
Weakness: CWE-347
Assigned by: disclosure@vulncheck.com

Dates

Published: 2026-06-29
Last modified: 2026-10-07
Added to KEV: 2026-06-29
Remediation due: 2026-07-02
Sources: CISA KEV, NVD

Affected products

Simple-Help Simplehelp- 5.5.16, 6.0

As listed in the NVD configuration data. Not a statement about your estate.