CriticalCVE-2024-20439

    Cisco Smart Licensing Utility Static Credential Vulnerability (CVE-2024-20439)

    Published In CISA KEV since Sources: SingCERT, pwn.watch, CVE.org

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    What is affected, what to do

    A vulnerability in Cisco Smart Licensing Utility (CSLU) could allow an unauthenticated, remote attacker to log into an affected system by using a static administrative credential. This vulnerability is due to an undocumented static user credential for an administrative account.

    The vulnerability is being actively exploited; treat it as a priority. Update smart_license_utility to version 2.3.0. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Cisco Smart License Utility eq 2.1.0..2.1.0
    • Cisco Smart License Utility eq 2.0.0..2.0.0
    • Cisco Smart License Utility eq 2.2.0..2.2.0

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    Metrics

    9.8

    Priority

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

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: SingCERT, pwn.watch, CVE.org

    97.1 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.89

    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
    234.93 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: CSA/SingCERT 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
    9.8 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
    9.8
    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“.

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    97.1 %
    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
    99.89
    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 31 March 2025
    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-912

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This CVE is on KEV because an undocumented static admin credential reduces the barrier to full CSLU API takeover to zero — network-reachable without authentication, trivially scriptable, and among the CVEs most likely to be exploited. Attackers use the API foothold to extract licensing data and pivot off CSLU hosts (typically admin workstations or jump servers) into management networks. Treat as critical wherever a vulnerable CSLU build runs anywhere on the estate — even a transient install is enough. Risk drops meaningfully if CSLU is not permanently running and port 8182 is loopback-bound only; full remediation requires 2.3.0.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade Cisco Smart Licensing Utility (CSLU) to 2.3.0 or later — affected versions are 2.0.0, 2.1.0 and 2.2.0. Pull the fixed build from the Cisco Software Center and deploy to every host where CSLU has ever been invoked.
      • Check whether CSLU is running as a persistent service. CSLU is not designed to run as a daemon — kill the process (cslu.exe on Windows, cslu on Linux) and disable autostart until patched. The flaw is only exploitable while the service is actively listening (TCP 8182).
      • Restrict network reachability on TCP 8182 immediately: bind to 127.0.0.1 only or block it entirely via host firewall and perimeter ACL. No reachability from client VLANs, DMZ, or the internet.
      • Hunt for prior exploitation on affected hosts: hits against the CSLU REST API (/cslu/v1/...), newly created local accounts, unexpected outbound connections from the CSLU process. On any hit, treat the host as compromised and trigger IR.
      • If CSLU was installed on an administrator workstation, rotate that admin's credentials after removal — API admin access on the host is a realistic springboard for lateral movement.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: place CSLU hosts into a management VLAN with no north-south exposure; permit TCP 8182 only on loopback or from named admin jump hosts. Add an explicit perimeter deny for inbound 8182/TCP.
      • Endpoint hardening: shut CSLU down after each licensing operation; do not run it as an autostart service. Documented operation is a manual, time-bounded launch by an admin.
      • IPS/WAF: block HTTP requests to /cslu/v1/scheduler/jobs, /cslu/v1/products and Basic-Auth headers carrying the publicly known default credential. Snort/Suricata rule: alert on request URI /cslu/v1/ to port 8182 originating anywhere other than loopback.
      • IAM: hosts running CSLU must not cache domain-admin or Tier-0 credentials. Launch CSLU under a dedicated low-privileged local user, never under a service account with domain rights.
      • Refresh the asset inventory: CSLU is frequently installed ad hoc on admin workstations and forgotten. Query software inventory (Intune, SCCM, osquery) for CSLU / cslu.exe and remove shadow installations.
      • Vulnerability scanning: enable a weekly credentialed scan with a signature for CVE-2024-20439 or CSLU < 2.3.0, because users will reinstall the tool on their own.

    3. Runbook step 3

      Detection rules

      • Network (Zeek/Suricata): alert on HTTP connections to TCP 8182 with URI prefix /cslu/v1/ from any source other than 127.0.0.1. Sigma shape: selection: dst_port: 8182, http.uri|startswith: '/cslu/v1/'.
      • Web/app log on the CSLU host: any HTTP 200 response to /cslu/v1/scheduler/jobs or /cslu/v1/products with a Basic-Auth header — any non-local request is suspect.
      • Sysmon EID 3 (Network Connect) for process cslu.exe with remote addresses outside the expected Cisco licensing backend (*.cisco.com). Unusual DNS/HTTP destinations in the CSLU process tree indicate API abuse.
      • EDR process ancestry: child processes of cslu.exe (particularly cmd.exe, powershell.exe, python.exe) are never expected in normal operation and should fire a high-severity alert.
      • KQL shape (Microsoft Defender/Sentinel): DeviceNetworkEvents | where LocalPort == 8182 and RemoteIP != "127.0.0.1" and InitiatingProcessFileName =~ "cslu.exe"
      • Auditd / Windows EID 4624 logon type 3: correlate new administrative sessions on CSLU-equipped hosts with network hits on port 8182.

    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

    A vulnerability in Cisco Smart Licensing Utility (CSLU) could allow an unauthenticated, remote attacker to log into an affected system by using a static administrative credential. This vulnerability is due to an undocumented static user credential for an administrative account. An attacker could exploit this vulnerability by using the static credentials to login to the affected system. A successful exploit could allow the attacker to login to the affected system with administrative rights over the CSLU application API.

    Source: CSA/SingCERT, pwn.watch, NVD (NIST), cvelistv5, 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
    CiscoCisco Smart License Utility
    • 2.2.0
    • 2.0.0
    • 2.1.0
    • —
    • —
    • —
    ciscosmart_license_utility
    • 2.0.0 – < 2.3.0
    • 2.3.0

    Vendors and products

    Weakness classes (CWE)

    • CWE-912Hidden Functionality

      Class

      The product contains functionality that is not documented, not part of the specification, and not accessible through an interface or command sequence that is obvious to the product's users or administrators.

      Entry at MITRE CWE-912

    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
    CSA/SingCERTActive Exploitation of Vulnerabilities in Cisco Smart Licensing Utility (opens in a new tab)CSA/SingCERTactively exploited

    References & sources

    • sec.cloudapps.cisco.comcisco-sa-cslu-7gHMzWmwVendor advisory, pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2024-20439government-resource, US government resource
    • pwn.watchpwn.watch: Cisco Smart Licensing Utility: Smart Licensing Utility Static Credential Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2024-20439pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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