CriticalCVE-2026-48558

    SimpleHelp Authentication Bypass via Missing OIDC JWT Signature Verification (CVE-2026-48558)

    Published Last modified In CISA KEV since Sources: CVE.org

    What is affected, what to do

    CVE-2026-48558 is an authentication bypass vulnerability in SimpleHelp's OIDC authentication flow. An unauthenticated remote attacker can submit forged tokens to obtain fully authenticated technician sessions, potentially bypassing multi-factor authentication. This affects SimpleHelp versions 5.5.15 and earlier, as well as 6.0 pre-release versions, and is actively exploited. Organizations should urgently upgrade to version 5.5.16 to mitigate the risk. The vulnerability is listed in the CISA KEV catalog with a high exploit maturity.

    The vulnerability is being actively exploited; treat it as a priority. Update SimpleHelp to version 5.5.16. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • SimpleHelp lt 5.5.0..5.5.16
    • SimpleHelp gte 6.0..*
    Fixed in
    • SimpleHelp 5.5.16

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    10.0

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    10.0

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org

    77.7 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.56

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    248.07 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    10.0 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    10.0
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.5
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    77.7 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.56
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 30 June 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-347

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication or user interaction. Its changed scope means a forged technician session effectively grants remote administrative control over every managed endpoint, not just the server. Remote-support platforms like SimpleHelp are a favoured initial-access route against MSPs and their downstream customers, because one server unlocks many organisations, and exploitation likelihood is markedly elevated. CISA does not flag ransomware use, but that should not lower urgency. Treat internet-exposed instances with OIDC enabled as critical and remediate within 24 hours. Instances without OIDC or without external exposure can follow the emergency patch cycle, including verification of third-party providers.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Identify every SimpleHelp server, including instances run by service providers or MSPs on your behalf, and record version and authentication setup. Affected are 5.5.15 and earlier plus all 6.0 pre-release builds. Only instances with OIDC login configured are exploitable, so triage those first.
      • Patch: Upgrade to SimpleHelp 5.5.16. For 6.0 pre-releases the context names no fixed build. A fix is available from the vendor; look up the version in the vendor advisory. Until then, take 6.0 pre-release instances off the internet or roll back to 5.5.16.
      • Disable OIDC if you cannot patch now: Fall back to local technician accounts with strong passwords and MFA. The flaw is missing signature validation on ID tokens. Per the advisory, an inactive OIDC flow is not exploitable.
      • Restrict exposure: Limit the technician login (the SimpleHelp server's HTTP/HTTPS interface) to VPN or admin networks at the perimeter firewall. Keep client connectivity only where operationally required.
      • Compromise assessment: Terminate all active technician sessions. Audit technician accounts, groups and permissions for unknown entries. Rotate API keys, server secrets and any credentials stored on the server. If compromise is suspected, preserve logs and the configuration directory before rebuilding.
      • Supply-chain check: If a provider runs SimpleHelp against your estate, get written confirmation of the patch level. Until you have it, stop the Remote Access service on your endpoints.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Place the server in a DMZ with tight egress. Allow outbound traffic only to your OIDC provider and the vendor update host. Expose the technician login solely via a zero-trust proxy or a device-checked VPN.
      • WAF/reverse proxy: Inspect requests to the OIDC callback endpoint. Block JWTs with an "alg":"none" header or an empty signature segment. For example, Base64 of {"alg":"none" starts with eyJhbGciOiJub25lIi. Also reject tokens whose iss does not match your IdP.
      • IAM/least privilege: Strip technicians of global client access, bulk-command rights and script execution unless needed. Enforce MFA inside SimpleHelp as well, not just at the IdP, since the advisory mentions MFA bypass.
      • Endpoint hardening: Use EDR or AppLocker rules to stop the SimpleHelp Remote Access service from launching script interpreters (cmd.exe, powershell.exe, wscript.exe, mshta.exe). Prefer attended over unattended access.
      • Configuration: Remove unused authentication providers. Do not bind the admin interface to the public NIC. Forward server logs to the SIEM.

    3. Runbook step 3

      Detection rules

      • SimpleHelp server / reverse-proxy logs: Look for successful OIDC technician logins with no matching sign-in event at the IdP (Entra ID sign-in logs, Keycloak events). Correlate on username within a ±5 min window. This is the strongest signal of forged tokens.
      • Web access logs: Look for requests to OIDC callback or login paths carrying JWTs with alg set to none, HS256 (where RS256 is expected) or an empty signature. Splunk example: index=proxy uri_path="*oidc*" | regex _raw="eyJhbGciOiJub25lIi|\.\s*$".
      • Technician session anomalies: Watch for logins from unfamiliar ASNs or countries, newly created technician accounts, permission changes, and bulk actions across many clients in a short window.
      • EDR process ancestry (Sysmon EID 1 / Defender DeviceProcessEvents): Look for a parent process in the JWrapper-Remote Access folder or Remote Access.exe spawning shells. KQL example: DeviceProcessEvents | where InitiatingProcessFolderPath has "JWrapper-Remote Access" and FileName in~ ("cmd.exe","powershell.exe","rundll32.exe").
      • Network (Zeek/Suricata): Look for new outbound connections from endpoints shortly after SimpleHelp sessions, such as payload downloads, secondary RMM tools or tunnelling utilities. Also watch for unusual outbound volume from the SimpleHelp server itself.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    SimpleHelp versions 5.5.15 and prior and 6.0 pre-release versions contain 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. No user interaction is required.

    Source: cvelistv5, NVD (NIST), CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    SimpleHelpSimpleHelp
    • 5.5.0 – < 5.5.16
    • ≥ 6.0
    • 5.5.16
    • —
    simple-helpsimplehelp
    • < 5.5.16
    • 6.0
    • 5.5.16
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-347Improper Verification of Cryptographic Signature

      Base

      The product does not verify, or incorrectly verifies, the cryptographic signature for data.

      Entry at MITRE CWE-347

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Reference tagged as exploithorizon3.ai (opens in a new tab)PoC (publicly reported)reported, not verified—
    PoC-in-GitHub (nomi-sec)CVE-2026-48558 (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • horizon3.aiattack-research/disclosures/cve-2026-48558-simplehelp-authentic…Technical description, Exploit
    • simple-help.comsecurity/simplehelp-security-update-2026-05Vendor advisory
    • simple-help.comrelease-newsRelease notes
    • blackpointcyber.comblog/a-djinn-in-the-machine-taskweavers-node-js-intrusion-chainThird-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-48558government-resource

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedVulnCheck

      Show 9 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://horizon3.ai/attack-research/disclosures/cve-2026-48558-simplehelp-authentication-bypass-iocs/
      Referenceadded
      —
      https://simple-help.com/release-news
      Referenceadded
      —
      https://simple-help.com/security/simplehelp-security-update-2026-05
      Referenceremoved
      https://horizon3.ai/attack-research/disclosures/cve-2026-48558-simplehelp-authentication-bypass-iocs/
      —
      Referenceremoved
      https://simple-help.com/release-news
      —
      Referenceremoved
      https://simple-help.com/security/simplehelp-security-update-2026-05
      —
      Reference typeremoved
      https://horizon3.ai/attack-research/disclosures/cve-2026-48558-simplehelp-authentication-bypass-iocs/ Types: Third Party Advisory
      —
      Reference typeremoved
      https://simple-help.com/release-news Types: Release Notes
      —
      Reference typeremoved
      https://simple-help.com/security/simplehelp-security-update-2026-05 Types: Patch, Vendor Advisory
      —

      Source identifier: disclosure@vulncheck.com

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: yes

      Show 8 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://blackpointcyber.com/blog/a-djinn-in-the-machine-taskweavers-node-js-intrusion-chain/
      Referenceadded
      —
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-48558
      Referenceremoved
      https://blackpointcyber.com/blog/a-djinn-in-the-machine-taskweavers-node-js-intrusion-chain/
      —
      Referenceremoved
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-48558
      —
      Reference typeremoved
      https://blackpointcyber.com/blog/a-djinn-in-the-machine-taskweavers-node-js-intrusion-chain/ Types: Technical Description, Third Party Advisory
      —
      Reference typeremoved
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-48558 Types: US Government Resource
      —
      SSVC assessmentremoved
      {"id":"CVE-2026-48558","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-06-12T00:00:00+00:00"}
      —
      SSVC assessmentadded
      —
      {"id":"CVE-2026-48558","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-06-30T03:55:22.397894Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    3. ReceivedVulnCheck

      CVSS V4.0: AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

      CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

      Weakness type: CWE-347

      Description added or changed

      Show 7 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      SimpleHelp versions 5.5.15 and prior and 6.0 pre-release versions contain 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. No user interaction is required.
      CVSSadded
      —
      AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
      Weakness type (CWE)added
      —
      CWE-347
      Referenceadded
      —
      https://horizon3.ai/attack-research/disclosures/cve-2026-48558-simplehelp-authentication-bypass-iocs/
      Referenceadded
      —
      https://simple-help.com/release-news
      Referenceadded
      —
      https://simple-help.com/security/simplehelp-security-update-2026-05

      Source identifier: disclosure@vulncheck.com

    Linked advisories

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