CVE-2021-40870

What it actually does

Aviatrix Controller 6.x before 6.5-1804.1922 allows unauthenticated attackers to upload a dangerous file type and use directory traversal to place it in an executable or otherwise sensitive path. Because the issue is reachable over the network without credentials or user interaction, successful exploitation can result in arbitrary code execution on the controller with the privileges of the affected application or web server process, enabling full compromise of controller confidentiality, integrity, and availability.

Why it matters to the business

Compromise of an Aviatrix Controller can give attackers control over a critical cloud networking management plane, potentially enabling network disruption, theft of cloud configuration data, pivoting into connected cloud environments, and manipulation of routing or VPN connectivity. The vulnerability is in CISA KEV, has a high EPSS likelihood score, and has been exploited in the wild, so internet-exposed or unpatched controllers should be treated as urgent exposure even though it is not specifically flagged by CISA as ransomware-used.

How an attack unfolds

An attacker identifies an exposed Aviatrix Controller running a vulnerable 6.x release, then sends a crafted unauthenticated upload request containing a server-executable payload or web shell. The request abuses insufficient file type restrictions and directory traversal sequences to write the uploaded file outside the intended upload directory and into a location where it can be executed or invoked by the web server/application. The attacker then requests or triggers the uploaded file, gaining command execution on the controller. From there, the attacker may establish persistence, collect Aviatrix configuration and credentials or keys available to the controller, modify networking settings, deploy additional tooling, and use the controller’s cloud connectivity and trust relationships to move laterally or disrupt operations.

How to fix it

Upgrade Aviatrix Controller to version 6.5-1804.1922 or later. If immediate upgrade is not possible, remove public internet exposure, restrict controller access to trusted administrative networks or VPNs, enforce strong network-layer allowlisting, and monitor/block unauthenticated upload attempts and path traversal patterns at the reverse proxy/WAF where feasible. Review the controller filesystem for unexpected uploaded executable files or web shells before returning the system to service. Because this is a known-exploited vulnerability, organizations should not rely on mitigation alone for long-term risk reduction.

How to confirm the fix worked

Confirm the controller is running Aviatrix Controller 6.5-1804.1922 or later and that no vulnerable 6.x instance remains reachable from untrusted networks. Validate exposure by checking external attack surface inventories, vulnerability scanners, cloud security posture tools, and direct administrative version checks. Attempt only safe, non-destructive validation: verify upload endpoints reject unauthenticated requests, block dangerous file extensions, and normalize/prevent directory traversal sequences. Review configuration to ensure management interfaces are not publicly accessible unless explicitly required and protected by network controls.

Typical attack path

1. Scan for internet-accessible Aviatrix Controller instances and fingerprint version or vulnerable behavior.
2. Send a crafted unauthenticated file upload request containing directory traversal sequences and a dangerous file type payload.
3. Write the payload to an executable web/application path instead of the intended upload location.
4. Invoke the uploaded payload to execute arbitrary commands on the controller.
5. Deploy a web shell, reverse shell, or post-exploitation tooling for persistence and interactive access.
6. Harvest controller configuration, cloud credentials, VPN material, logs, and network topology information.
7. Use controller privileges or cloud trust relationships to pivot, alter routes/security settings, or disrupt cloud network connectivity.

How to detect it

Review Aviatrix Controller web access logs, application logs, system logs, reverse proxy/WAF logs, EDR telemetry, and shell/process execution records for evidence of unauthenticated upload activity followed by execution. Look for requests to upload endpoints containing directory traversal patterns such as ../ or URL-encoded equivalents, dangerous file extensions such as .php, .jsp, .war, .sh, .py, .pl, or .cgi, and subsequent HTTP GET/POST requests to newly created files in web-accessible paths. On the host, search web/application directories, temporary upload directories, and controller application paths for recently created executable files, web shells, or files with timestamps near suspicious upload requests. Investigate unexpected child processes spawned by web server or application service accounts, including shells, curl/wget, Python, Perl, nc/netcat, bash, sh, or reverse-shell behavior. Correlate with outbound connections to unfamiliar IPs, new scheduled tasks or cron jobs, modified startup scripts, changed controller configuration, newly added users, and unusual cloud API activity initiated shortly after suspicious controller access.

• ../
• ..%2f
• %2e%2e%2f
• ..%252f
• %2e%2e/
• /etc/passwd
• .php
• .jsp
• .war
• .cgi
• .sh
• .pl
• .py
• multipart/form-data
• filename="../
• filename="..%2f
• filename="%2e%2e%2f
• cmd=
• /bin/sh
• /bin/bash
• bash -c
• sh -c
• curl
• wget
• nc -e
• netcat
• python -c
• perl -e
• php -r
• chmod +x
• crontab -e
• /tmp/
• /var/tmp/
• /var/www/
• /var/www/html/
• /opt/aviatrix/
• /home/admin/
• POST

What your security team should do

• Treat any vulnerable internet-facing Aviatrix Controller as a high-priority incident-response candidate due to known exploitation and CISA KEV listing with a 2022-02-01 remediation deadline.
• Upgrade all Aviatrix Controller deployments to 6.5-1804.1922 or later; if exact fixed build tracking is unavailable, upgrade to the latest supported release.
• Immediately restrict management-plane access to trusted administrative IP ranges or private connectivity and remove unnecessary public exposure.
• Hunt for evidence of prior exploitation, including suspicious upload requests, path traversal strings, unexpected executable files in web-accessible directories, and anomalous child processes spawned by web/application services.
• Rotate credentials, API keys, cloud access keys, VPN keys, and secrets accessible to the controller if exploitation is suspected or cannot be ruled out.
• Review Aviatrix and cloud networking configuration changes around the suspected exposure window for unauthorized route, tunnel, account, or security policy modifications.
• Add SIEM detections for unauthenticated upload attempts containing traversal sequences or executable file extensions targeting Aviatrix Controller endpoints.
• Preserve logs and forensic images before cleanup if suspicious artifacts are found.