CriticalCVE-2018-11138

    Quest KACE System Management Appliance Remote Command Execution Vulnerability (CVE-2018-11138)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    An attacker can exploit an authentication bypass to perform remote code execution on the Quest KACE System Management Appliance. This vulnerability is actively exploited in ransomware campaigns since 2022. All versions up to 8.0.318 are affected. Immediate patching to the latest version is critical to mitigate this risk. The CVE is listed in the CISA KEV catalog, highlighting the urgency of addressing this vulnerability.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Quest KACE System Management Appliance eq 8.0.318..8.0.318

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

    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: CVE.org

    91.7 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.81

    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
    253.70 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 exploited
    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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    91.7 %
    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
    99.81
    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 21 March 2022
    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-78

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is exploitable over the network without authentication or user interaction. It yields full code execution on an appliance whose job is to push privileged software to the entire client fleet, which makes it an ideal foothold and distribution channel for ransomware. CISA flags it for known ransomware campaign use, and its exploitation likelihood sits among the very highest of all tracked CVEs. Treat an exposed, unpatched SMA as a top-priority emergency on par with a compromised domain controller. Patch internal-only instances within days as well, because of their lateral-spread potential.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Check exposure and restrict it now: Determine whether the KACE System Management Appliance (SMA) web interface is reachable from the internet or from untrusted segments (typically TCP 80/443). Restrict access to /common/download_agent_installer.php and the admin UI to management networks via firewall or reverse proxy.
      • Apply the vendor patch: Version 8.0.318 is confirmed affected. A patch is available from the vendor — look up the fixed version in the Quest vendor advisory. Move appliances on outdated major releases to a supported, patched build.
      • Assess compromise before patching: Preserve web server logs and an appliance snapshot before patching or rebooting destroys evidence. This flaw dates back to 2018, so treat any appliance that was exposed while unpatched as potentially compromised.
      • Audit distribution features for abuse: Review all scripts, Managed Installations and software deployment packages created or modified in recent weeks. Disable anything unrecognised immediately. The appliance pushes code to every endpoint with SYSTEM/root privileges.
      • Rotate credentials: Once the appliance is clean, reset SMA admin accounts, stored domain and service accounts (LDAP bind, agent provisioning credentials) and API tokens.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Place the SMA in a dedicated management VLAN. Allow web UI access only from admin jump hosts and agent traffic only from client networks. Restrict appliance egress to vendor update destinations via an allowlist.
      • WAF / reverse-proxy rule: Block requests to /common/download_agent_installer.php from unauthorised source networks. Also drop any request carrying shell metacharacters in parameters (;, |, `, $(, %3B, %7C, %60, %24%28).
      • IPS signature: Deploy a Suricata/Snort rule along the lines of http.uri; content:"/common/download_agent_installer.php"; pcre:"/[;|]|$(|%3B|%7C|%60/i"` and alert on matches as critical.
      • Client endpoint hardening: Use EDR or AppLocker/WDAC policy to stop KACE agent processes from spawning script interpreters with encoded or downloaded payloads. For example, block powershell -enc, mshta and rundll32 with URL arguments as children of the agent.
      • Least privilege: Trim SMA admin roles, enforce MFA on the admin UI, and give the appliance's domain accounts scoped, delegated rights rather than Domain Admin.

    3. Runbook step 3

      Detection rules

      • SMA web access log: Look for GET or POST requests to /common/download_agent_installer.php with unusual parameters or shell metacharacters, and for any such request from an external IP. SPL: index=web uri_path="/common/download_agent_installer.php" | regex uri_query="(;|\||%3B|%7C|%60|\$\()".
      • Process ancestry on the appliance (where shell or syslog access exists): The web server or PHP process spawning sh, fetch, curl, wget, nc or perl is a strong command-injection indicator.
      • Sysmon EID 1 / EDR on managed Windows clients: KACE agent binaries (e.g. AMPAgent.exe, runkbot.exe) spawning powershell.exe, cmd.exe /c, vssadmin, wbadmin or bcdedit. Sigma shape: ParentImage|endswith: '\runkbot.exe' AND Image|endswith: ['\powershell.exe','\vssadmin.exe','\wbadmin.exe'].
      • Network telemetry (Zeek/Suricata): New outbound connections from the SMA IP to unknown external hosts, especially long-lived sessions or downloads shortly after hits on the vulnerable script (reverse shell, tool staging).
      • Windows Event ID 4624/4672: Logons by SMA service accounts on hosts outside their normal pattern, such as domain controllers or backup servers.

    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

    The '/common/download_agent_installer.php' script in the Quest KACE System Management Appliance 8.0.318 is accessible by anonymous users and can be abused to execute arbitrary commands on the system.

    Source: CISA KEV Catalog, cvelistv5, NVD (NIST)

    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
    questkace_system_management_appliance
    • 8.0.318
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

      Base

      The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

      Entry at MITRE CWE-78

    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
    Exploit-DBEDB-ID 44950 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—

    References & sources

    • exploit-db.com44950Exploit, x_refsource_EXPLOIT-DB
    • coresecurity.comadvisories/quest-kace-system-management-appliance-multiple-vuln…x_refsource_MISC
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2018-11138government-resource
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