CriticalCVE-2021-1497

    Cisco HyperFlex HX Command Injection Vulnerabilities (CVE-2021-1497)

    Published In CISA KEV since Sources: CVE.org

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    What is affected, what to do

    A cluster of vulnerabilities in the web-based management interface of Cisco HyperFlex HX allows an unauthenticated, remote attacker to perform command injection attacks. These vulnerabilities enable command execution with root privileges on affected devices. They are actively exploited, as evidenced by their inclusion in the CISA KEV list. Affected products include versions 4.0(2e) to 4.5(2a) of the Cisco HyperFlex HX Data Platform. Immediate updating to the latest secure version is imperative.

    The vulnerability is being actively exploited; treat it as a priority. Update Cisco HyperFlex HX-Series to version 4.0\(2e\), Cisco HyperFlex HX-Series to version 4.5\(2a\). Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Cisco HyperFlex HX-Series lt *..4.0\(2e\)
    • Cisco HyperFlex HX-Series lt 4.5..4.5\(2a\)
    Fixed in
    • Cisco HyperFlex HX-Series 4.0\(2e\)
    • Cisco HyperFlex HX-Series 4.5\(2a\)

    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

    99.92 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.97

    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
    228.95 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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    99.92 %
    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
    99.97
    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 8 November 2024
    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 vulnerability is on KEV because it yields unauthenticated remote code execution as root through a web UI — no credentials, no user interaction, only network reach to the management interface. EPSS places it among the CVEs most likely to be exploited and public exploit code is readily available; even without documented ransomware use, the appliance is a prime pivot into virtualisation and storage backbones. Treat as critical for any organisation still running HyperFlex Installer VMs online, particularly where the management network is reachable from office or OT segments; if internet-exposed, raise an immediate P1 incident.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory all Cisco HyperFlex HX Data Platform Installer VMs and patch to a fixed release: 4.0 to 4.0(2e), 4.5 to 4.5(2a). Branches 3.5 and 4.0 before 2e are not patched per Cisco's advisory — plan a migration to a supported train.
      • Remove the Installer VM's web management interface (TCP/443, TCP/8443) from any network segment that does not strictly need it. Restrict access to a dedicated admin jump-host VLAN; add perimeter deny rule for installer-vm:443/8443.
      • Power off or delete Installer VMs that are no longer actively used — the installer is designed as a transient appliance and should not remain permanently reachable on the network.
      • Rotate credentials on every HyperFlex cluster whose Installer VM may have been exposed (vCenter service account, HX admin, controller SSH keys). Assume root-level compromise where exploitation is suspected and rebuild from a known-good image.
      • Capture forensic artefacts (memory snapshot, disk image) of affected Installer VMs before rebuilding if there is any indication of exploitation.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: strictly isolate the HyperFlex management VLAN from user and server VLANs; only admin jump hosts may reach 443/8443 on the Installer VM. Enforce via core-switch ACLs and NSX/ACI microsegmentation where available.
      • Place a WAF or reverse proxy in front of the Installer UI and block payload patterns suggesting command injection in URL parameters and POST bodies (shell metacharacters ;, |, `, $(, &&, URL-encoded variants %3B, %7C).
      • Deploy Talos Snort/Suricata signatures for CVE-2021-1497/1498 (SID series per Cisco advisory) in inline mode on perimeter and east-west sensors.
      • IAM hardening: minimise local admin accounts on the Installer VM, allow SSH only with keys, disable password login. Enforce MFA on the upstream jump host.
      • Egress filtering: whitelist outbound destinations from the Installer VM (Cisco update URLs, internal repository) to break reverse shells and second-stage payload retrieval.

    3. Runbook step 3

      Detection rules

      • Inspect webserver/reverse-proxy logs for POST requests to Installer endpoints containing shell metacharacters in the body. Sigma shape: selection: cs-uri-stem contains '/' AND cs-method='POST' AND cs-body matches '.*(;|\|\||&&|\$\(|).*'`.
      • Auditd/Sysmon on the Installer VM: process ancestry where tomcat, java or the web daemon spawns sh, bash, python, nc, curl or wget is highly suspicious. KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ('java','tomcat') and FileName in~ ('sh','bash','nc','curl','wget','python').
      • Network telemetry (Zeek conn.log): new outbound connections from the Installer VM IP to external hosts, especially on uncommon ports (4444, 1337, 8080) — classic reverse-shell indicator.
      • File-system monitoring for writes to /tmp, /var/tmp, /dev/shm executed in the web-process context; new executables in those paths are a red flag.
      • Correlate auth logs for root-level command execution without a preceding interactive login (compare last output against /var/log/secure and wtmp).

    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

    Multiple vulnerabilities in the web-based management interface of Cisco HyperFlex HX could allow an unauthenticated, remote attacker to perform command injection attacks against an affected device. For more information about these vulnerabilities, see the Details section of this advisory.

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

    Vendors and products

    Affected operating systems

    Affected operating systems
    Otherciscohyperflex_hx_data_platform—

    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
    Packet StormCisco HyperFlex HX Data Platform Command Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • tools.cisco.com20210505 Cisco HyperFlex HX Command Injection VulnerabilitiesVendor advisory, x_refsource_CISCO, Vendor advisory
    • packetstormsecurity.comfiles/162976/Cisco-HyperFlex-HX-Data-Platform-Command-Execution…x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1497government-resource, US government resource
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