CriticalCVE-2026-18556

    Unauthenticated administrative account takeover (CVE-2026-18556)

    Published Last modified In CISA KEV since Sources: ASD ACSC, pwn.watch, BSI, CVE.org

    What is affected, what to do

    Authentication bypass using an alternate path or channel vulnerability in N-able N-central allows Authentication Bypass. This issue affects N-central: through 2026.1.

    The vulnerability is being actively exploited; treat it as a priority. Update N-Central to version 2026.3.1.7. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • N-able N-central lte *..2026.1

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

    Metrics

    8.2

    Priority

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

    Source: NVD, CVSS v4

    7.4

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: ASD ACSC, pwn.watch, BSI, CVE.org

    7.9 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 94.7

    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
    234.91 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), ASD ACSC 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
    8.2 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
    7.4
    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
    8.2
    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
    7.9 %
    Moderate — model estimates 1-10% exploitation likelihood.
    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
    94.7
    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
    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-288

    Response and mitigation

    Why act now?

    Prioritisation rationale

    N-central is an RMM platform with privileged reach into every managed endpoint. An authentication bypass therefore hands attackers potential control over an entire fleet or an MSP's whole customer base. That makes this flaw a prime vector for initial access, supply-chain compromise and follow-on software deployment. It is network-reachable without authentication or user interaction. The elevated attack complexity offers little comfort once exploitation is confirmed in practice, and its exploitation likelihood ranks well above most CVEs. CISA has no known ransomware use on record, but RMM compromise is a well-established precursor to such campaigns. Treat internet-exposed instances and MSP deployments as critical with remediation within 24 h. Internal-only, segmented instances should be patched as a high priority in the next maintenance window.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Cut exposure now: Restrict internet access to the N-central web console and API (typically HTTPS/443) to known admin IPs or VPN at the perimeter firewall. Keep the agent communication path reachable only where remote agents require it, and scope it as tightly as possible.
      • Patch: All N-central versions through 2026.1 are affected. A fix is available from the vendor — check the N-able advisory for the fixed version. Snapshot or back up the server before updating to preserve forensic evidence.
      • Hunt before returning to normal operations: Export the N-central audit log covering recent weeks. Review logins, newly created users, role changes, API tokens, new automation policies, scripts and software deployment jobs.
      • Rotate credentials: Reset all N-central accounts, especially admins and service accounts. Also rotate API keys and every credential stored in N-central, such as domain credentials used for discovery and push install, SNMP credentials and hypervisor logins.
      • Address supply-chain impact: MSPs should notify affected customer tenants. Internal IT operators should treat all managed endpoints as potentially at risk until the review is complete. An RMM compromise equals remote code execution across the managed estate.
      • Check NIS2 reporting: If you find evidence of exploitation, the 24 h early warning to BSI or your national CSIRT applies.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Place the N-central server in a dedicated management segment. Allow admin access only via a jump host or PAW. Allowlist outbound traffic from the server to update servers and the services it actually needs.
      • Reverse proxy / WAF: Front the console with an authenticating reverse proxy, for example IdP pre-authentication with MFA. This stops an alternate authentication path before requests reach the application. Block legacy, SOAP or API paths from external sources where they are not operationally required.
      • IAM / least privilege: Enforce MFA or SSO on all N-central accounts. Minimise the number of global admins. Disable local accounts that bypass the IdP.
      • Configuration hardening: Limit arbitrary script and remote command execution to approved, signed scripts. Require dual approval for critical automation policies where feasible.
      • Endpoint layer: Enable EDR rules on managed hosts that block, or at least alert on, unusual child processes of the N-central agent. This contains the blast radius if the server itself falls.

    3. Runbook step 3

      Detection rules

      • N-central audit log / web access log: Look for successful sessions or API calls with no preceding normal login event, and for access from source IPs outside the admin allowlist. Example SPL: index=ncentral sourcetype=access_combined status=200 NOT src_ip IN (<admin_allowlist>) | stats count by src_ip, uri_path
      • Administrative changes: Alert on new users, role changes, new API tokens and new or modified scripts or policies outside change windows. Forward these events to the SIEM via syslog or log export.
      • EDR process ancestry (Sysmon EID 1 / Windows 4688): Watch for the agent process (e.g. agent.exe) spawning powershell.exe, cmd.exe, rundll32.exe or certutil.exe, especially with encoded commands or downloads. Example KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "agent.exe" and FileName in~ ("powershell.exe","cmd.exe","rundll32.exe") and ProcessCommandLine has_any ("-enc","http","DownloadString")
      • Fan-out execution: Watch for the same command launched on many endpoints within a short window. A typical example is an identical command line on more than 20 hosts within 10 minutes. This is the classic pattern of RMM abuse for payload deployment.
      • Network telemetry (Zeek/Suricata): Flag new outbound connections from the N-central server to unknown destinations, and unusual egress volumes that could indicate exfiltration of the customer or asset database. Also monitor inbound HTTPS sessions from previously unseen ASNs.

    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

    Authentication bypass using an alternate path or channel vulnerability in N-able N-central allows Authentication Bypass. This issue affects N-central: through 2026.1.

    Source: ASD ACSC (CC BY 4.0), pwn.watch, BSI CSAF, BSI WID Portal, NVD (NIST), CISA KEV Catalog, cvelistv5

    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
    N-ableN-central
    • ≤ 2026.1
    • —
    n-ablen-central
    • ≤ 2026.1
    • —
    N-ableN-Central
    • < 2026.3.1.7
    • 2026.3.1.7

    Vendors and products

    Weakness classes (CWE)

    • CWE-288Authentication Bypass Using an Alternate Path or Channel

      Base

      The product requires authentication, but the product has an alternate path or channel that does not require authentication.

      Entry at MITRE CWE-288

    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
    ASD ACSCActive exploitation of remote monitoring and management platform within Australia (opens in a new tab)ASD ACSCactively exploited
    PoC-in-GitHub (nomi-sec)ncentral-compromise-ioc-triage (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • uptime.n-able.comN-able N-central — CVE-2026-18556Vendor advisory, pwn-watch
    • n-able.comblog/n-central-security-update-august-2-2026Vendor advisory, Vendor advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-18556government-resource, US government resource
    • pwn.watchpwn.watch: N-able N-central: N-able N-central Authentication Bypass Using an Alternate Path or Channel Vulnerabilitypwn-watch
    • documentation.n-able.comN-able N-central — CVE-2026-18577pwn-watch
    • NVD (NIST)NVD: CVE-2026-18577pwn-watch
    • NVD (NIST)NVD: CVE-2026-18556pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

    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. NVD analysis modifiedNVD

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Reference typeadded
      —
      CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-18556 Types: US Government Resource

      Source identifier: nvd@nist.gov

    2. Record modifiedCISA ADP

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

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-18556
      SSVC assessmentchanged
      {"id":"CVE-2026-18556","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-04T13:10:59.591524Z"}
      {"id":"CVE-2026-18556","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-04T17:42:08.190557Z"}

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

    3. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: yes

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://www.n-able.com/blog/n-central-security-update-august-2-2026
      SSVC assessmentchanged
      {"id":"CVE-2026-18556","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-08-03T16:48:46.194108Z"}
      {"id":"CVE-2026-18556","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-04T13:10:59.591524Z"}

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

    4. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-18556","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-08-03T16:48:46.194108Z"}

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

    5. Receiveda5532a13…

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

      Weakness type: CWE-288

      Description added or changed

      Show 5 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      N-central
      Descriptionadded
      —
      Authentication bypass using an alternate path or channel vulnerability in N-able N-central allows Authentication Bypass. This issue affects N-central: through 2026.1.
      CVSSadded
      —
      AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/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
      Weakness type (CWE)added
      —
      CWE-288
      Referenceadded
      —
      https://uptime.n-able.com/

      Source identifier: a5532a13-c4dd-4202-bef1-e0b8f2f8d12b

    One NVD translation into another language is hidden.

    Linked advisories

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2026-18556
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-18556"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-18556.svg?lang=en" alt="CVE-2026-18556 – NEOSEC Intel" height="20"></a>