CVE-2021-42129

What it actually does

CVE-2021-42129 is a command injection vulnerability in Ivanti Avalanche before version 6.3.3. An attacker who can authenticate to or otherwise access the Avalanche Inforail Service with low privileges can inject operating-system commands into service-side processing and cause the Avalanche server to execute those commands. Because the flaw is network-reachable, low-complexity, and requires no user interaction, successful exploitation can provide high-impact compromise of confidentiality, integrity, and availability on the host running the affected service.

Why it matters to the business

A compromised Ivanti Avalanche deployment can give an attacker control over infrastructure used to manage mobile and ruggedized endpoint fleets. This can lead to theft of operational data, disruption of warehouse, logistics, retail, or field-device management workflows, tampering with device configurations, and use of the Avalanche server as a foothold for broader network intrusion. The high EPSS score indicates meaningful likelihood of exploitation activity in the wild even though it is not currently listed in CISA KEV, so internet-exposed or broadly reachable Avalanche services should be treated as high priority.

How an attack unfolds

An attacker first identifies an Ivanti Avalanche server exposing the Inforail Service. The attacker obtains or uses existing low-privileged access to interact with the service. They then submit crafted input containing shell metacharacters or command syntax that the vulnerable service passes to the underlying operating system without sufficient validation or escaping. The injected command runs in the security context of the Avalanche service process. From there, the attacker may execute reconnaissance commands, write web shells or tools, create persistence, dump credentials, alter Avalanche-managed device configurations, or pivot to other internal systems.

How to fix it

Upgrade Ivanti Avalanche to version 6.3.3 or later. If immediate upgrade is not possible, restrict network access to the Inforail Service to trusted administrative hosts only, place the service behind VPN or management-network controls, block access from untrusted networks, and disable the service if it is not required. Review and reduce privileges of the account running Avalanche services where supported. Rotate credentials that may have been accessible from the Avalanche server if compromise is suspected. After patching, restart affected services and verify that all Avalanche components are running the updated version.

How to confirm the fix worked

Confirm the installed Ivanti Avalanche version is 6.3.3 or later through the product console, installed-program inventory, package metadata, or vendor-supported version command. Validate that the Inforail Service is not reachable from untrusted networks using network scanning from representative external and internal segments. Attempt only safe, authorized validation using vendor guidance or a controlled security test; do not use destructive command-injection payloads in production. Confirm that EDR or operating-system telemetry shows no unexpected child processes spawned by Avalanche or Inforail service processes after the upgrade.

Typical attack path

1. Identify an Ivanti Avalanche deployment running a version earlier than 6.3.3.
2. Confirm network access to the Avalanche Inforail Service.
3. Use low-privileged credentials or otherwise authorized access to reach the vulnerable service function.
4. Send crafted input that includes operating-system command syntax.
5. Execute initial commands such as user, host, network, and privilege discovery.
6. Deploy additional tooling or scripts under the service account context.
7. Attempt credential theft, lateral movement, configuration tampering, or service disruption.

How to detect it

To determine whether exploitation already occurred, review application logs for Ivanti Avalanche and the Inforail Service around suspicious access times, focusing on unusual requests, malformed parameters, shell metacharacters, encoded payloads, or unexpected administrative actions. Correlate with operating-system and EDR telemetry for command execution by Avalanche or Inforail service processes. On Windows, review Security Event ID 4688 process-creation logs if enabled, Sysmon Event ID 1, PowerShell Operational logs, service-creation events, scheduled-task events, and antivirus/EDR detections. Look for Avalanche service processes spawning command shells, PowerShell, Windows Script Host, download utilities, network discovery tools, credential-access tools, or archive utilities. Review network flow and proxy logs for outbound connections from the Avalanche server to unfamiliar external hosts shortly after Inforail Service requests. Investigate new local users, new services, new scheduled tasks, modified Avalanche configuration, unexpected files in application directories or temporary directories, and evidence of lateral movement from the Avalanche server.

• Inforail Service
• cmd.exe /c
• powershell.exe -enc
• powershell.exe -EncodedCommand
• wscript.exe
• cscript.exe
• certutil.exe -urlcache
• bitsadmin /transfer
• curl.exe http
• wget.exe http
• whoami
• ipconfig /all
• net user
• net localgroup administrators
• nltest /domain_trusts
• net view
• schtasks /create
• sc create
• reg add
• rundll32.exe
• mshta.exe
• Avalanche
• Ivanti Avalanche

What your security team should do

• Prioritize upgrade of all Ivanti Avalanche servers to 6.3.3 or later, especially systems reachable from broad internal networks or the internet.
• Restrict access to the Inforail Service using host firewalls, network ACLs, VPN requirements, and management-network segmentation.
• Hunt for suspicious child processes, script interpreters, archive tools, download utilities, or discovery commands spawned by Avalanche-related services.
• Review Avalanche administrative accounts and service accounts for least privilege; rotate credentials if suspicious activity is found.
• Collect and preserve Avalanche application logs, Windows Event Logs, EDR telemetry, and network flow data before remediation if exploitation is suspected.
• Monitor for repeated failed or unusual access attempts to the Inforail Service and for command-execution behavior from the Avalanche server.
• Add the vulnerability to asset-management and vulnerability-management exception tracking until all affected instances are confirmed remediated.