CriticalCVE-2021-40870

    Aviatrix Controller Unrestricted Upload of File (CVE-2021-40870)

    Published In CISA KEV since Sources: CVE.org

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    What is affected, what to do

    An unauthenticated attacker can achieve remote code execution (RCE) through directory traversal by exploiting the unrestricted file upload vulnerability in Aviatrix Controller 6.x versions before 6.5-1804.1922. This vulnerability is actively exploited in the wild and has been reported in ransomware campaigns since 2022. Affected products include versions from 6.2 to 6.5. An immediate update to version 6.5-1804.1922 or later is urgently required to mitigate this risk.

    The vulnerability is being actively exploited; treat it as a priority. Update Aviatrix Controller to version 6.2.2043, Aviatrix Controller to version 6.3.2490, Aviatrix Controller to version 6.4.2838. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Aviatrix Controller lt 6.2..6.2.2043
    • Aviatrix Controller lt 6.3..6.3.2490
    • Aviatrix Controller lt 6.4..6.4.2838
    • Aviatrix Controller lt 6.5..6.5.1922
    Fixed in
    • Aviatrix Controller 6.2.2043
    • Aviatrix Controller 6.3.2490
    • Aviatrix Controller 6.4.2838
    • Aviatrix Controller 6.5.1922

    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

    93.0 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.83

    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
    228.73 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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    93.0 %
    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
    99.83
    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 4 February 2025

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is unauthenticated and network-reachable, and it yields remote code execution on a device that administers the entire multi-cloud network — a Controller compromise effectively hands over routing, firewall policy, and cloud credentials for the full Aviatrix deployment. Exploitation likelihood is among the highest in the KEV catalogue, public exploit code (including a Metasploit module) has existed since 2021 and is routinely used in mass scans. For NIS2-regulated operators running Aviatrix this is a crown-jewel asset: priority P1, patch or isolate within 24 hours regardless of change window. The absence of a CISA ransomware flag suggests data exfiltration and persistent cloud access are more likely objectives than encryption.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade Aviatrix Controller to a fixed release immediately: 6.2.2043, 6.3.2490, 6.4.2838, or 6.5.1922 (a.k.a. 6.5-1804.1922). Follow Aviatrix's documented upgrade path and snapshot the Controller VM beforehand.
      • Pull the Controller management interface (TCP/443 web UI/API) off the public internet right now. Allow access only via VPN, bastion host, or a dedicated admin VLAN — this bug is unauthenticated and network-reachable.
      • Review the Controller's web access logs (nginx/apache) for the past 90 days for POST requests carrying file uploads and path-traversal patterns (../, URL-encoded %2e%2e%2f). Treat any hit as a compromise.
      • After patching, or on any suspicion, rotate every secret the Controller holds: cloud provider API keys (AWS/Azure/GCP), admin passwords, SAML/OIDC signing keys, gateway certificates. These credentials typically carry very broad rights across the cloud tenant.
      • Inspect all connected Aviatrix Gateways for unexpected configuration changes or new firewall rules; cross-check gateway logs against the Controller audit trail.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: move the Controller into a dedicated management VLAN and restrict ingress to defined admin jump hosts via source-IP allowlists on the security group, NSG, or perimeter firewall.
      • Place a WAF or reverse proxy in front and drop requests containing traversal sequences, multiple URL-encodings, and multipart/form-data uploads to unexpected endpoints. Reject upload bodies carrying .py, .php, .jsp, or .sh extensions.
      • Egress filtering from the Controller: restrict outbound traffic to the minimum required for cloud API calls and Aviatrix update servers. This blocks reverse shells to arbitrary internet hosts.
      • Harden the Controller VM: enable file-integrity monitoring (AIDE/Tripwire) on the web root and /home/ubuntu, alert on any new executable file.
      • IAM least privilege: trim the cloud role (IAM role, managed identity, service account) used by the Controller down to the actions it truly needs — no *:*, no org-wide admin. This caps the blast radius if RCE still lands.
      • Enforce MFA for admin logins and forward Controller audit logs via syslog/CEF to the SIEM; do not rely on local-only logging.

    3. Runbook step 3

      Detection rules

      • Controller web access logs: POST requests to paths such as /v1/backend1 or /v1/api combined with ../ or %2e%2e in body or query string. Sigma shape: selection.cs-method: POST AND cs-uri-stem|contains: "../".
      • Process telemetry (auditd / Sysmon-equivalent on Linux): web server account (apache, www-data, ubuntu) spawning shells (/bin/sh, /bin/bash), interpreters (python, perl), or network tools (curl, wget, nc) with parent process httpd/nginx/gunicorn — a strong IOC chain.
      • auditd SYSCALL execve where ppid is a web server process and exe is outside the normal Controller binary set — alert.
      • Network telemetry (Zeek/Suricata): outbound connections from the Controller to destinations not on the allowlist, especially ports 4444, 1337, 8080, or Tor entry nodes.
      • Filesystem monitoring: new files in upload paths with executable extensions or a #! shebang at the start of the file. KQL shape: DeviceFileEvents | where FolderPath has "aviatrix" and FileName endswith_any (".py",".sh",".php").

    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

    An issue was discovered in Aviatrix Controller 6.x before 6.5-1804.1922. Unrestricted upload of a file with a dangerous type is possible, which allows an unauthenticated user to execute arbitrary code via directory traversal.

    Source: 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
    aviatrixcontroller
    • 6.4 – < 6.4.2838
    • 6.2 – < 6.2.2043
    • 6.5 – < 6.5.1922
    • 6.3 – < 6.3.2490
    • 6.4.2838
    • 6.2.2043
    • 6.5.1922
    • 6.3.2490

    Vendors and products

    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 StormAviatrix Controller 6.x Path Traversal Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • docs.aviatrix.comHowTos/UCC_Release_Notes.htmlx_refsource_MISC, Release notes, Vendor advisory
    • wearetradecraft.comadvisories/tc-2021-0002x_refsource_MISC, Exploit, Third-party advisory
    • packetstormsecurity.comfiles/164461/Aviatrix-Controller-6.x-Path-Traversal-Code-Execut…x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40870government-resource, US government resource
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